I’ve seen a lot of posts like these but most of them only go up to season 6 and/or exclude episodes that I think are pretty important so… as somebody who’s been watching Adventure Time since it first aired, here’s my ultimate must-watch episode guide!

I’ve included all the episodes that are relevant to the larger plot (as well as a few particularly heartwarming “filler” episodes) and all of them are annotated so that you can know in advance exactly what they contribute to the series.

You can watch seasons 1-9 on Hulu and find most of the episodes on Dailymotion. The blog madridista-again has also posted direct downloads of a lot of the episodes from season 8 and onward. In addition, if you download the extension Hola, you may be able to watch some of the episodes on Netflix.

Season 1

• S1E1 – Slumber Party Panic – Introduces main cast
• S1E2 – Trouble in Lumpy Space – Introduces Lumpy Space Princess
• S1E3 – Prisoners of Love – Introduces Ice King
• S1E4 – Tree Trunks – Introduces Tree Trunks
• S1E5 – The Enchiridion! – Introduces the Enchiridion
• S1E7 – Ricardio the Heart Guy – Introduces Ricardio
• S1E9 – My Two Favorite People – Introduces Tiffany, further development for Jake and Lady Rainicorn
• S1E10 – Memories of Boom Boom Mountain – Further development for Finn
• S1E12 – Evicted! – Introduces Marceline
• S1E15 – What Is Life? – Introduces NEPTR, further development for Ice King
• S1E16 – Ocean of Fear – Further Development for Finn
• S1E20 – Freak City – Introduces Magic Man
• S1E22 – Henchman – Further development for Marceline
• S1E24 – What Have You Done? – Further development for Princess Bubblegum
• S1E25 – His Hero – Introduces Billy

Season 2

• S2E1 – It Came from the Nightosphere – Introduces Hunson, further development for Marceline
• S2E8 – Crystals Have Power – Further development for Tree Trunks
• S2E10 – To Cut a Woman’s Hair – Further development for Finn
• S2E11 – The Chamber of Frozen Blades – Further development for Gunter
• S2E12 – Her Parents – Further development for Lady Rainicorn
• S2E15 – The Real You – Further development for Finn and Princess Bubblegum
• S2E17 – Death in Bloom – Further development for Peppermint Butler, introduces Death
• S2E18 – Susan Strong – Introduces Susan, further development for Finn
• S2E20 – Go With Me – Further development for Finn and Marceline
• S2E22 – The Limit – Introduces the Ancient Psychic Tandem War Elephant, further development for Jake
• S2E23 – Video Makers – Further development for Finn, Jake, and BMO
• S2E24 – Mortal Folly – Introduces The Lich, contributes to later plot
• S2E25 – Mortal Recoil – Introduces The Lich, contributes to later plot (continued)
• S2E26 – Heat Signature – Further development for Marceline and Lumpy Space Princess

Season 3

• S3E3 – Memory of a Memory – Further development for Marceline
• S3E5 – Too Young – Introduces Lemongrab, further development for Finn and Princess Bubblegum
• S3E6 – The Monster – Further development for Lumpy Space Princess
• S3E7 – Still – Further development for Ice King
• S3E8 – Wizard Battle – Introduces Abracadaniel, further development for Finn and Princess Bubblegum
• S3E9 – Fionna and Cake – Introduces the Fionna and Cake universe
• S3E10 – What Was Missing – Further development for Finn, Jake, Princess Bubblegum, and Marceline
• S3E11 – Apple Thief – Introduces Mr. Pig, further development for Tree Trunks
• S3E12 – The Creeps – Further development for Finn
• S3E13 – From Bad to Worse – Sequel to S1E1
• S3E14 – Beautopia – Further development for Susan and Finn
• S3E17 – Thank You – Technically a filler but one of the cutest episodes in the series so watch it anyway
• S3E18 – The New Frontier – Introduces the Cosmic Owl
• S3E19 & S3E20 – Holly Jolly Secrets – Further development for Ice King
• S3E21 – Marceline’s Closet – Further development for Marceline
• S3E25 – Dad’s Dungeon – Introduces Joshua, further development for Finn
• S3E26 – Incendium – Introduces Flame Princess, further development for Finn

Season 4

• S4E1 – Hot to the Touch – Further development for Flame Princess and Finn
• S4E4 – Dream of Love – Further development for Tree Trunks and Mr. Pig
• S4E5 – Return to the Nightosphere – Further development for Hunson and Marceline
• S4E6 – Daddy’s Little Monster – Further development for Hunson and Marceline
• S4E7 – In Your Footsteps – Contributes to later plot
• S4E10 – Goliad – Introduces Goliad, further development for Princess Bubblegum
• S4E13 – Princess Cookie – Further development for Princess Bubblegum
• S4E15 – Son of Mars – Further development for Magic Man
• S4E16 – Burning Low – Further development for Flame Princess, Finn, and Princess Bubblegum
• S4E18 – King Worm – Further development for Finn
• S4E19 – Lady & Peebles – Further development for Princess Bubblegum and Lady Rainicorn
• S4E20 – You Made Me – Further development for Lemongrab
• S4E22 – Ignition Point – Further development for Flame Princess and Finn
• S4E24 – Reign of Gunters – Introduces Wizard City, further development for Finn, Gunter, and Ice King
• S4E25 – I Remember You – Further development for Marceline and Ice King
• S4E26 – The Lich – Further development for Finn, Princess Bubblegum, and Billy, contributes to later plot

Season 5

• S5E1 – Finn the Human – Introduces Prismo, further development for Finn, Marceline, and Ice King, contributes to later plot
• S5E2 – Jake the Dog – Further development for Finn, Jake, Marceline, and Ice King, contributes to later plot
• S5E5 – All the Little People – Further development for Finn
• S5E6 – Jake the Dad – Introduces Jake’s kids, further development for Jake and Lady Rainicorn
• S5E9 – All Your Fault – Further development for Lemongrab
• S5E11 – Bad Little Boy – Extension of the Fionna and Cake universe
• S5E12 – Vault of Bones – Further development for Flame Princess and Finn
• S5E14 – Simon & Marcy – Further development for Ice King and Marceline
• S5E17 – BMO Lost – Further development for BMO
• S5E20 – Shh! – Another high quality filler episode
• S5E21 – The Suitor – Further development for Princess Bubblegum
• S5E23 – One Last Job – Further development for Jake
• S5E24 – Another Five More Short Graybles – Further development for Jake Jr. and Lemongrab
• S5E26 – Wizards Only, Fools – Further development for Princess Bubblegum
• S5E27 – Jake Suit – Further development for Finn, Jake, and Flame Princess
• S5E28 – Be More – Further development for BMO
• S5E29 – Sky Witch – Introduces Maja, further development for Marceline and Princess Bubblegum
• S5E30 – Frost & Fire – Further development for Finn and Flame Princess
• S5E31 – Too Old – Introduces Lemonhope, further development for Finn, Lemongrab, and Princess Bubblegum
• S5E32 – Earth & Water – Further development for Princess Bubblegum, Flame Princess, Finn, and Cinnamon Bun
• S5E34 – The Vault – Introduces Shoko, further development for Finn and Princess Bubblegum
• S5E38 – Red Starved – Further development for Marceline
• S5E40 – Play Date – Further development for Ice King and Abracadaniel, contributes to plot of following episode
• S5E41 – The Pit – Continuation of previous episode
• S5E42 – James – Introduces James, further development for Princess Bubblegum
• S5E43 – Root Beer Guy – Introduces Root Beer Guy
• S5E44 – Apple Wedding – Introduces the King of Ooo, further development for Tree Trunks, Mr. Pig, and Princess Bubblegum
• S5E45 – Blade of Grass – Further development for Finn, contributes to later plot
• S5E46 – Rattleballs – Introduces Rattleballs, further development for Princess Bubblegum
• S5E47 – The Red Throne – Further development for Flame Princess and Cinnamon Bun
• S5E48 – Betty – Further development for Betty and Ice King
• S5E50 & S5E51 – Lemonhope – Further development for Lemonhope
• S5E52 – Billy’s Bucket List – Further development for Finn, contributes to later plot

Season 6

• S6E1 – Wake Up – Introduces Martin, further development for Finn, contributes to later plot
• S6E2 – Escape from the Citadel – Introduces Sweet P, further development for Finn, contributes to later plot
• S6E3 – James II – Sequel to S5E42
• S6E4 – The Tower – Further development for Finn
• S6E6 – Breezy – Further development for Finn
• S6E10 – Something Big – Further development for Maja, Root Beer Guy, and the Ancient Psychic Tandem War Elephant.
• S6E12 – Ocarina – Further development for Kim Kil Whan and Jake
• S6E15 – Nemesis – Further development for Princess Bubblegum
• S6E16 – Joshua & Margaret Investigations – Further development for Joshua, Margaret, and Jake
• S6E19 – Is That You? – Further development for Prismo
• S6E20 – Jake the Brick – High quality filler episode
• S6E21 – Dentist – Further development for Tiffany
• S6E22 – The Cooler – Further development for Flame Princess and Princess Bubblegum
• S6E23 – The Pajama War – Further development for Princess Bubblegum and Finn
• S6E24 – Evergreen – Major lore/worldbuilding episode
• S6E25 – Astral Plane – Further development for Finn
• S6E26 – Gold Stars – Further development for Sweet P
• S6E27 – The Visitor – Further development for Finn and Martin
• S6E28 – The Mountain – Further development for Lemongrab
• S6E29 – Dark Purple – Further development for Susan
• S6E30 – The Diary – Further development for TV
• S6E33 – Jermaine – Further development for Jake and Jermaine
• S6E38 – You Forgot Your Floaties – Further development for Magic Man and Betty
• S6E39 – Be Sweet – Further development for Sweet P
• S6E40 – Orgalorg – Further development for Gunter
• S6E41 – On the Lam – Further development for Finn and Martin
• S6E42 – Hot Diggity Doom – Contributes to later plot
• S6E43 – The Comet – Further development for Finn, contributes to later plot

Season 7

• S7E1 – Bonnie & Neddy – Introduces Neddy, further development for Princess Bubblegum
• S7E2 – Varmints – Further development for Marceline and Princess Bubblegum
• S7E3 – Cherry Cream Soda – Further development for Root Beer Guy
• Stakes Miniseries – Major development for Marceline, contributes to later plot (I highly recommend watching all of this)
• S7E14 & S7E15 – The More You Moe, the Moe You Know – Further development for BMO
• S7E21 – King’s Ransom – Further development for Betty
• S7E23 – Crossover – Further development for Finn, resolves conflict from Season 5
• S7E25 – Flute Spell – Further development for Finn and Huntress Wizard
• S7E26 – The Thin Yellow Line – Further development for Princess Bubblegum

Season 8

• S8E1 – Broke His Crown – Further development for Ice King, Betty, Marceline, and Princess Bubblegum
• S8E2 – Don’t Look – Further development for Finn
• S8E4 – Lady Rainicorn of the Crystal Dimension – Further development for Lady Rainicorn
• S8E5 – I Am a Sword – Further development for Finn
• S8E6 – Bun Bun – Further development for Finn, Flame Princess, and Cinnamon Bun
• S8E7 – Normal Man – Further development for Magic Man
• S8E8 – Elemental – Introduces Patience, further development for Princess Bubblegum
• S8E10 – The Music Hole – Introduces the Music Hole, further development for Finn
• S8E11 – Daddy-Daughter Card Wars – Further development for Jake and Charlie
• S8E12 – Preboot – Introduces Dr. Gross, further development for Susan and Tiffany
• S8E13 – Reboot – Introduces Fern, further development for Susan and Finn
• S8E14 – Two Swords – Further development for Finn and Fern
• S8E15 – Do No Harm – Further development for Fern and Susan
• S8E16 – Wheels – Introduces Bronwyn, further development for Jake
• S8E17 – High Strangeness – Further development for Tree Trunks and Princess Bubblegum
• S8E19 – Jelly Beans Have Power – Further development for Princess Bubblegum
• Island Miniseries – Major development for Finn, contributes to later plot (I highly recommend watching all of this)

Season 9

• S9E1 – Orb – Contributes to later plot
• Elements Miniseries – Major development for Ice King and Betty, contributes to later plot (I highly recommend watching all of this)
• S9E10 – Abstract – Further development for Jake
• S9E11 – Ketchup – Further development for Marceline
• S9E13 – Whispers – Further development for Sweet P and Fern
• S9E14 – Three Buckets – Further development for Finn and Fern, contributes to later plot

Season 10

• S10E1 – The Wild Hunt – Further development for Finn and Huntress Wizard, contributes to later plot
• S10E2 – Always BMO Closing – Further development for BMO and Ice King, contributes to later plot.
• S10E3 – Son of Rap Bear – Further development for Flame Princess
• S10E4 – Bonnibel Bubblegum – Introduces Gumbald, further development for Princess Bubblegum
• S10E5 – Seventeen – Further development for Finn, contributes to later plot
• S10E7 – Marcy & Hunson – Further development for Hunson and Marceline
• S10E8 – The First Investigation – Further development for Jake
• S10E10 – Jake the Starchild – Further development for Jake
• S10E11 – Temple of Mars – Further development for Betty and Magic Man, finale leadup
• S10E12 – Gumbaldia – Finale leadup
• S10E13 – Come Along With Me – That’s the finale babes!!