The episode do many lines in it. You must have 4 made up characters but you can use only 4 only characters from the show. Do many lines because when others reply it will be an episode.

I Want It Back - A fire monster saw Finn holding its gem, and asks him to give it back. Jake accidentally break it. They must find 6 gems to replace it or pay the price (their life).

Finn : Hey Jake! Look at this gem. (shows him a purple shining gem)
Jake : Wow, dude! Where ya get it?
Finn : I found it under my bed. (Jake holds the gem) Careful! It is fragile.
Fira : (enters the room) Hey guys. What's up?
Finn : Fira! We found this shining gem.
Fira : That gem looks familiar.
Jake : What's the matter with it, Fira the scientist?
Fira : I don't know.
PB : (enters the room) Hey Fira, there you are! We're not done with the experiment yet.
Fira :PB, doesn't that gem look familiar?
PB :Yeah. (a giant fire eyeball appeared at the window) Huh? (PB, Fira, Finn and Jake walk to the window)
Fire monster : You are holding my gem!!

Finn : What? This is my gem!
Jake : Yeah. Finders keepers.
Fire monster : It is my gem.
Fira : Finn, where did you find this gem?
Flame Prince : Beware that monster!!!
Finn : Is this really it's gem?
Flame Prince : Yes!! (takes the gem from Jake)
Jake : (stretches his arms and holds the gem)Let me give him. (the gem falls down and it breaks)
Fire monster : Ugh! Look what you did! Repay me with 6 gems or pay the price which is your life!

-cuts to them walking to an underground cave-
Finn : Where are we going?
Fira : Marceline, Caitlyn, Dean and Fabian are experts in finding gems.
Finn : Vampires are expert in gems?
PB :Yes, sciencetifically,
Fabian : (appears) What are you doing here?
Jake : We need you and the others experts on gems.
Fabian : Gems? Why?
Fira : Because we need 6 gems or pay the price.
Flame Prince : Which is our lives.
Fabian : No.
Finn : Oh man!
PB : Fira.
Fira : (gives Fabian money) Money from Earth.
Fabian : Human money! Okay! I'll get the others!

The Lost Princess:
(Finn and Jake wonder around the house)
Finn: Hey Jake, this looks awkward..
Jake: It is very fun, actually.
(Glacier appears)
Glacier: Hi!
Finn and Jake: Hello!
Finn: What is your name?
Glacier: Glacier.. Say, you are the heroes of ooo right?
Finn: Yeah.. I'm Finn!
Jake: I'm Jake!
Glacier: Nice to meet you, two... I really need your help..
Finn: What is it?
Glacier: Can you show me the way to the Ice Kingdom?
Jake: Sure thing!
(At the Ice Kingdom)
Finn: Brrrr... It's cold here!
Jake: Yeah.. Wait.. Glacier? You're not cold?!
Glacier: Nah... Show me the way to ICE KING!
Finn and Jake: Ice King?!
(At Ice King's castle..)
Ice King: Who goes there?!

TO BE CONTINUED.....
SORRY!! I WAS TIRED......

I like all your episodes. I am gonna make a new idea and post it here.