What is Life? is the 15th episode in Season 1 of Adventure Time. It first aired on June 14th, 2010.
To help pull a prank on Jake when Finn was pranked by Jake with a bag of Butter, Finn creates NEPTR but when created, it turns out NEPTR wasn't fully functional, so Finn needed more power. After taking some from Ice King, problems come and NEPTR must solve them.
While Finn is playing video games, Jake shows up and and acts strangely while holding a big trash bag. Jake then throws the big trash bag filled with butter at Finn. Finn gets disappointed because he didn't see that prank coming. He goes near Jake and states that he will make a prank better than Jake. Then Jake says that he wants to take a nap. Finn tries to think a prank that is better than the butter surprise because he thinks there is no prank better than that. He then gets an idea to prank Jake by throwing to Jake never-ending pies.
In the garage, Finn makes the never-ending pie-throwing robot while singing. After he makes the finishing touch, he tries to activate it but it doesn't work. Finn then throws it out, the robot got struck by lightning and comes to life. The robot calls Finn as its creator and introduces itself as NEPTR, short for Never-Ending Pie-Throwing Robot. As Finn is ready to prank Jake, NEPTR complaints that it is not fully functional and has technical problems. Finn didn't want to see his robot suffer 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. NEPTR whispers loudly and Finn asks him to keep quiet. Ice King then comes in to the room where Finn and NEPTR is. He is wearing his underpants and is seen talking to one of his penguins. He then goes to his comfortable chair and play video games.
Gunter notices Finn and Jake and it follows them, causing Ice King's computer destroyed. Ice King as really mad about that. Finn and NEPTR manage to sneak through the room where Ice King is.
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.
In the imagination zone, 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.
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.
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 screaming Jake as he wakes up.
- It is revealed that Finn has a wallet in this episode.
- The captions in the book that Finn read for a prank did not match the pictures. The caption of the pie was "Yo Whaddup".