What is Life?

"What is Life?" is episode fifteen in season one of Adventure Time.

Synopsis
When Jake pranks Finn, Finn decides to prank Jake back by creating a robot that throws pies. The robot, however, has a few problems, and Finn goes to Ice King's lightning storage to give NEPTR (short for Never-Ending Pie Throwing Robot) some of the king's lightning. However, when he does this NEPTR develops some of Ice King's personality and he has to choose between pranking with Finn or capturing princesses with Ice King.

Plot
While Finn is playing video games, Jake shows up with a big trash-bag and throws it at Finn, showing that the bag was full of butter. Finn wants to get back at Jake and decides to build a robot that will throw pies at Jake, who then takes a nap. But the robot doesn't work and Finn throws it out, but then it comes to life when it was struck by lightning. The robot calls Finn its creator and introduces itself as NEPTR, short for Never-Ending Pie-Throwing Robot. As Finn is ready to prank Jake, he realizes that NEPTR has some technical problems, and decides to help his robot by going to the Ice Kingdom to get more lightning bolts from Ice King.

Finn and NEPTR get to the Ice Kingdom by Balloons, who are revealed to be grade-A pranksters. They sneak through Ice King's castle while he is talking to one of his penguins named Gunter and playing video games. However, they trigger Ice King's alarm and are being chased by an Ice Bull. Finn and NEPTR make it to Ice King's lightning bolt storage, but it gets destroyed by Ice King and his Ice-o-pede. As Ice King is going to strike lightning on Finn, the blast hits NEPTR and he gains his full capacity. NEPTR throws pies at the Ice-o-pede and he and Finn escape on the Balloons, but begins acting strange. Ice King notices it too and follows them back to Finn's home.

When Finn gets NEPTR ready to prank Jake, NEPTR says he wants to capture princesses instead. Finn gets concerned about NEPTR's new behavior and when he opens the door, Ice King is there and kicks Finn away, then freezes him. Ice King decides to raise NEPTR as his son, revealing that Ice King's lightning blast gave NEPTR some of his personality. Ice King then takes NEPTR, along with Finn who uses his free hand to go with them, to Ice King's imagination zone, where he shows NEPTR all the beautiful princesses he can capture if he decides to be his son. They go back to the real world, and Finn breaks out of his frozen imprisonment, and then fights Ice King. After a short battle, they both decide that they should let NEPTR choose who to be with. NEPTR chooses Ice King, but reveals that he only choose Ice King to prank on, and throws a pie at Ice Kings face. Ice King is furios and attempts to shoot NEPTR and kill him. Finn jumps and screams "NEVER" and kicks Ice King, causing him to fall to the ground and knock out. Finn and NEPTR then leave Ice King to go prank on Jake, and Ice King dreams of him and NEPTR standing in the sunset, dreaming that NEPTR is his son.This suddenly causes a tear to come from Ice King.

Characters

 * Finn
 * Jake
 * Neptr
 * Ice King
 * Balloons
 * Gunter
 * Ice-o-pede

Minor characters

 * Ice Toads
 * Ice Bull
 * Video Game Girl
 * Video Game Frog
 * Video Game Flies

Cameo appearances

 * Snail

In Ice King's Imagination Zone

 * Bee Princess
 * Embryo Princess
 * Ghost Princess
 * Emerald Princess
 * Engagement Ring Princess
 * Jungle Princess
 * Lumpy Space Princess
 * Mini Queen
 * Muscle Princess
 * Nut Princess
 * Princess Bubblegum
 * Princess Princess Princess
 * Purple Princess
 * Space Angel Princess
 * Orange Princess
 * Turtle Princess
 * Wildberry Princess
 * Zombie Princess

Trivia

 * This episode was originally called "Ice King and Son".
 * Gunter makes her first appearance in this episode.
 * The Balloons, who made their debut in "Ricardio the Heart Guy", are grade "A" pranksters.
 * This is one of the few times that Jake is absent for much of the episode.
 * While Finn is building Neptr, he sings the Never Ending Pie Song without being auto-tuned, unlike his previous singing performances which have been.
 * All of the princesses make brief cameos in this episode, but only in Ice King's Imagination Zone.
 * Frederator Studios released a character design image that shows all the princesses that appear in this episode. Among them are several princesses that had not yet been shown in other episodes, including Turtle Princess, Nut Princess, Bumblebee Princess, Embryo Princess and Zombie Princess. All of them (with the exception of Reptile Princess) would reappear in the season two episode "Loyalty to the King".
 * Two main princesses did not appear in Ice King's Imagination Zone: Slime Princess and Hot Dog Princess.
 * This is the first instance that Finn and Jake's garage is seen.
 * The Balloons appeared to have a suicidal attitude as one of them said, "Finally! We can die!" Cartoon Network rarely displays death as humor in a kids show.
 * In this episode, Finn's cheeks are fat when he talks sometimes, and his eyebrows were shown through the episode.
 * In this episode, Finn's nose is seen, which is a rare occurrence, as the character designers do not usually draw noses on Finn.
 * When Finn is building Neptr, he attaches the robot arm to the upper side. However, when Neptr comes to life, the arm is moved lower to make room for the face.
 * When Finn is reading the book for have a better idea to prank Jake, a thief girl appears, which may be a reference to Penny from the episode "City of Thieves".