Latest episodes will be added soon, though they are almost all important to the plot now.
Forked from: https://gist.github.com/austinpray/175309550bf31dd6b904
Which started from here: https://www.reddit.com/r/adventuretime/comments/2vt41x/adventure_time_episode_list_recommended_episodes/
Episodes marked with * have only some plot important elements.
Episodes marked with ** have almost none or none plot importance but probably are interesting fillers.
| Season | Episode | Title | Reason | |
|---|---|---|---|---|
| 1 | 5 | The Enchiridion | A good intro to the series, plus introduces the important Enchiridion | |
| 1 | 8 | Business Time* | First mention of Ooo being post-apocalyptic | |
| 1 | 9 | My Two Favorite People | Intros the Jake and LR plotline | |
| 1 | 10 | Memories of Boom Boom Mountain | A look at how Finn was adopted into Jake's Family | |
| 1 | 12 | Evicted! | Intros Marceline | |
| 1 | 16 | Ocean of Fear | Introduces Finn's phobia | |
| 1 | 22 | Henchman* | Establishes Finn and Marceline as friends | |
| 1 | 23 | Rainy Day Daydream* | good episode to show someone who’s never seen the show before | |
| 1 | 25 | His Hero | introduces the Lich and Billy | |
| 2 | 1 | It Came from the Nightosphere | Significant to Marceline's Personal Plotline | |
| 2 | 12 | Her Parents | Continuation of Jake and LR Storyline | |
| 2 | 17 | Death in Bloom | Separates the Nightosphere from the Dead Worlds | |
| 2 | 18 | Susan Strong* | Significant for Susan's Possible Humanity | |
| 2 | 22 | The Limit* | Jake Character Development | |
| 2 | 24 | Mortal Folly | Lich Plotline | |
| 2 | 23 | Mortal Recoil | Lich Plotline | |
| 3 | 3 | Memory of Memory | Introduces Hambo, some of Marcy’s backstory | |
| 3 | 5 | Too Young* | Princess Bubblegum Background and wrapping up 2, Finale, Intro to Lemongrab plot | |
| 3 | 9 | Fionna and Cake* | A fan favorite | |
| 3 | 10 | What Was Missing | important characterization | |
| 3 | 12 | The Creeps* | Hints to future episode | |
| 3 | 14 | Beautopia* | Continues Susan Strong story line | |
| 3 | 19 | Holly Jolly Secrets 1 | Ice King and Mushroom War Plot | |
| 3 | 20 | Holly Jolly Secrets 2 | Ice King and Mushroom War Plot | |
| 3 | 25 | Dad's Dungeon | Finn and Jake Background | |
| 3 | 26 | Incendium Pt.1* | Flame Princess Plot Intro | |
| 4 | 1 | Hot to the Touch* | Flame Princess Subplot | |
| 4 | 2 | Five Short Graybles* | For the Exploded map of Earth in the Intro | |
| 4 | 5 | Return to the Nightosphere | Marceline Background | |
| 4 | 6 | Daddy's Little Monster | Marceline Background | |
| 4 | 7 | In Your Footsteps* | Lich Plot at End | |
| 4 | 10 | Goliad* | Finn and PB character development, maybe a returning plot? | |
| 4 | 15 | Sons of Mars | Introduces GGGG | |
| 4 | 16 | Burning Low* | Flame Princess Plot | |
| 4 | 18 | King Worm* | Hints to future events | |
| 4 | 20 | You Made Me* | Lemongrab Plot | |
| 4 | 22 | Ignition Point* | Flame Princess Plot | |
| 4 | 25 | I Remember You | Marceline and Simon Plot | |
| 4 | 26 | The Lich Pt.1 | Lich Plot | |
| 5 | 1 | Finn The Human | Lich Plot and Mushroom War | |
| 5 | 2 | Jake The Dog | See Above | |
| 5 | 3 | Frost and Fire* | Flame Princess Plot | |
| 5 | 6 | Jake the Dad | Jake and Lady Rainicorn Plot | |
| 5 | 9 | All Your Fault* | Lemongrab Plot | |
| 5 | 11 | Bad Little Boy* | Insight into Marceline and Ice King's day-to-day relationship, continution of Fionna and Cake subplot | |
| 5 | 12 | Vault of Bones* | Flame Princess Plot | |
| 5 | 14 | Simon and Marcy | Simon and Marceline Plot, Mushroom War | |
| 5 | 16 | Puhoy* | Flame Princess Plot | |
| 5 | 23 | One Last Job | Jake's past | |
| 5 | 24 | Another Five More Short Graybles* | Some slight plot elements that come back | |
| 5 | 28 | Be More* | B, MO backstory | |
| 5 | 21 | the Suitor* | Princess Bubblegum Character Development | |
| 5 | 29 | Sky Which | Reclaiming Hambo | |
| 5 | 31 | Too Old* | Finn finally gives up on PB, Lemongrab Plot, Intro to Lemonhope | |
| 5 | 32 | Earth and Water* | Flame Princess Plot | |
| 5 | 43 | Root Beer Guy* | Slight plot elements | |
| 5 | 34 | The Vault* | Princess Bubblegum background story | |
| 5 | 38 | Red Starved* | A Possible insight into Marceline and PB's relationship. | |
| 5 | 40 | Play Date* | Finn Character Development | |
| 5 | 41 | The Pit* | Finn Character Development | |
| 5 | 45 | Blade of Grass | Finn Character Development | |
| 5 | 46 | Rattleballs | Finn Character Development | |
| 5 | 47 | The Red Throne* | Flame Princess Plot | |
| 5 | 48 | Betty | Ice King/Simon Plot | |
| 5 | 50 | Lemonhope Pt.1 | Lemonhope Plot | |
| 5 | 51 | Lemonhope Pt.2 | Lemonhope Plot | |
| 5 | 52 | Billy’s Bucket List* | Intro to Finn’s dad plot | |
| 6 | 1 | Wake Up | Finn’s Dad plot | |
| 6 | 2 | Escape from the Citadel | Finn’s dad plot | |
| 6 | 3 | The Tower* | Finn Character Development | |
| 6 | 6 | Breezy | Finn Character Development | |
| 6 | 10 | Something Big* | Perhaps the beginning of a returning plot? | |
| 6 | 16 | Joshua & Margaret Investigations | Jake’s backstory | |
| 6 | 19 | Is That You? | Prismo Plot | |
| 6 | 22 | The Cooler* | Flame Princess Plot | |
| 6 | 24 | Evergreen | Ice King Plot | |
| 6 | 25 | Astral Plane | Finn’s dad plot | |
| 6 | 25 | Gold Stars | Lich Plot | |
| 6 | 26 | The visitor | Finn’s dad Plot | |
| 6 | 27 | The Mountain* | Some Finn/FP and Lemongrab characterization | |
| 6 | 28 | Dark Purple* | Susan Strong Plot | |
| 6 | 33 | Jermaine* | Finn and Jake family development | |
| 6 | 35 | Graybles 1000+* | Hints to future events | |
| 6 | 36 | Hoots | Cosmic owl character development; Hints to Gunter's identity | |
| 6 | 38 | You Forgot Your Floaties | Betty comeback; Magic man plot | |
| 6 | 39 | Be Sweet* | Hint for the Comet | |
| 6 | 40 | Orgalorg | Introduces Orgalorg | |
| 6 | 41 | On the Lem | Finn's Dad plot | |
| 6 | 42 | Hot Diggity Doom | Princess Bubblegum; King of Ooo; the Comet | |
| 6 | 43 | The Comet | The Comet (duh); Orgalorg; Finn's Dad | |
| 7 | 1 | Bonnie & Neddy | King of Ooo; Candy Kingdom; PB's brother | |
| 7 | 2 | Varmints | PB and Marceline development and some background story | |
| 7 | 3 | Cherry Cream Soda* | Root Beer Guy plot (Root Beer Guy episode was included in the original list so I'm including this one) | |
| 7 | 4 | Mama Said* | Canyon comeback | |
| 7 | 5 | Football* | BMO and Football; Football's life | |
| 7 | 6 | Marceline The Vampire Queen (1) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 7 | Everything Stays (2) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 8 | Vamps About (3) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 9 | Empress Eyes (4) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 10 | May I Come In? (5) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 11 | Take Her Back (6) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 12 | Checkmate (7) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 13 | The Dark Cloud (8) | Awesome Marceline plot and background story across 8 episodes | |
| 7 | 14 | The More You Moe (1) | MOs backstory | |
| 7 | 15 | The Moe You Know (2) | MOs backstory | |
| 7 | 16 | Summer Showers* | Viola story | |
| 7 | 21 | King's Ransom | Ice King; Gunter and Betty | |
| 7 | 23 | Crossover | Farmworld development; the Lich and Ice Finn | |
| 7 | 24 | Hall of Egress** | Just Wowed - Not a main plot | |
| 7 | 25 | Flute Spell* | Huntress Wizard; Finn's flute playing | |
| 7 | 26 | The Thin Yellow Line** | Banana Guards and PB - Not much main plot | |
| 7 | 26 | Broken His Crown | Some of Ice King's crown backstory + more Betty; PB and Marceline | |
| 7 | 28 | Don't Look* | How Finn sees some characters | |
| 7 | 30 | Lady Rainicorn of the Crystal Dimension* | Some Lady background story and T.V. development | |
| 7 | 31 | I Am a Sword | Sword Finn development | |
| 7 | 32 | Bun Bun* | Some FP and Finn development; Flame King development | |
| 7 | 33 | Normal Man | Magic Man; GGGG and Mars plot | |
| 7 | 34 | Elemental | Patience intro; History of the Elementals; Flashbacks from before the Lich Explosion | |
| 7 | 36 | The Music Hole | Finn Sword development | |
| 7 | 37 | Daddy-Daughter Card Wars* | Some Jake background story; Charlie development | |
| 7 | 38 | Pre-boot | Humans backstory; Susan development; Tiffany comeback | |
| 7 | 39 | Reboot | Susan development; Finn Sword and Grass Sword development | |
| 8 | 1 | Two Swords | Grass Finn development | |
| 8 | 2 | Do No Harm | Grass Finn becomes Fern the Human | |
| 8 | 3 | Wheels | Jake's granddaughter | |
| 8 | 4 | High Strangeness | Tree Trunks and PB's relationship; Tree Trunks' space family; PB's space program | |
| 8 | 5 | Horse and Ball** | James Backster - Non a main plot but kinda fun | |
| 8 | 6 | Jelly Beans Have Power | PB's elemental powers; Patience comeback | |
| 8 | 7 | Islands Part 1: The Invitation | Susan Strong and Humans backstory; the Departure | |
| 8 | 8 | Islands Part 2: Whipple the Happy Dragon* | The Guardian; Arrival at an Island | |
| 8 | 9 | Islands Part 3: Mysterious Island | Some Human backstory; Alva and the Islands | |
| 8 | 10 | Islands Part 4: Imaginary Resources | Better Reality | |
| 8 | 11 | Islands Part 5: Hide and Seek | Humans and Susan backstory; Susan remembers her past | |
| 8 | 12 | Islands Part 6: Min & Marty | Finn's parents' backstory | |
| 8 | 13 | Islands Part 7: Helpers | The New Human World | |
| 8 | 14 | Islands Part 8: The Light Cloud | Back to Ooo | |
| 9 | 1 | Orb | The New Ooo | |
| 9 | 2 | Elements Part 1: Skyhooks | Candy Kingdom; The New Ooo | |
| 9 | 3 | Elements Part 2: Bespoken For | What happened in Finn and Jake's absence; Betty comeback | |
| 9 | 4 | Elements Part 3: Winter Light | Ice Kingdom; Getting Betty | |
| 9 | 5 | Elements Part 4: Cloudy | Chilling Haircuts; the Plan | |
| 9 | 6 | Elements Part 5: Slime Central | Slime Kingdom; Jake Dies | |
| 9 | 7 | Elements Part 6: Happy Warrior | Flame Kingdom; Finn Turns | |
| 9 | 8 | Elements Part 7: Hero Heart | LSP Save; All Jewels Are Gathered; Betty's plan | |
| 9 | 9 | Elements Part 8: Skyhooks II | The Fifth Element | |
| 9 | 10 | Abstract | Jake development |
