What is Life?

Synopsis
Finn creates a Never-Ending Pie Throwing Robot (N.E.P.T.R.) to prank Jake, but it unexpectedly comes to life! Yet when he decides to use some of the Ice King's power to further develop it, this ultimately leads to a moral dilemma for the new living machine.

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. The robot doesn't work and Finn throws it out, but then it comes to life when it's 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 Neptr, Finn attempts to block it, but 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 Neptr begins acting strange, claiming to have added poison to his boysenberry pies. Ice King notices it too and follows them back to Finn's home.

When Finn gets Neptr ready to prank Jake, Neptr says he has a desire to capture princesses. 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 the Ice King shows Neptr all the beautiful princesses he can capture if he decides to be the Ice King's son, claiming to desire his allegiance because he can mate with robot princesses. 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 chooses Ice King to prank, and throws a pie at Ice King's face. Ice King is furious 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 pass out. Finn and Neptr then leave Ice King to go prank Jake, while Ice King dreams of him and Neptr watching the sunset, dreaming that Neptr is his son. This suddenly causes a tear to come from Ice King as the sounds of Neptr and Finn throw the never ending pies at Jake as he wakes up.

Major characters

 * Finn
 * Ice King
 * Neptr

Minor characters

 * Balloons
 * BMO
 * Ice Bull
 * Ice Toads
 * Jake
 * Snail
 * Video Game Frog
 * Video Game Girl

In Ice King's imagination zone

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

Music

 * Never Ending Pie Song

Trivia

 * This episode is where Gunter first appears.
 * Out of all the princesses listed above that appeared in Ice King's imagination zone, only the first six had been on the show before. This was the debut episode for fourteen new princesses.
 * Three known princesses did not appear in Ice King's Imagination Zone: Slime Princess, Hot Dog Princess, and Raggedy Princess.
 * A larger portion of Ice King's castle is revealed in this episode.
 * Ice King has a room where he keeps a surplus of lightning.
 * This is the first episode to show the Tree Fort's storage room.
 * The avatar in the video game the Ice King is playing is wearing a crown similar to Princess Bubblegum's.
 * Though the Ice King steals princesses, the Mini Queen is present.
 * The magazine Ice King is reading when the alarm sounds is called XOXXL.

Errors

 * At the end of Ice King's dream where he watches the sunset with Neptr, Neptr's face is shown to be on the wrong side. Originally his face is left of the microwave door. This time, however, it is shown on the right.
 * 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.

Production notes

 * This episode was originally called "Ice King and Son."

Videos
"What is Life?" Animatic|Animatic