Princess Bubblegum = The creators weren't expecting a "love relationship" going on in the beginning of the series. This show is called Adventure Time, so they wanted to start off with adventures and not lovey-dovey stuff. Anyways, a 13 year old hooking up with a 18 year old wasen't really age appropriate I guess.
Marceline = I think Marceline was supposed to be more of a challange for Finn and Jake, not a love intrest. Anyways, Marceline dosen't appear in alot of episodes anymore, so we cant learn much more aboout her past such in the episode "Memory of a memory", where we see Marceline with her ex, and her with her dad at the restraunt as her dad was eating her fries. Anyways, Marceline would never hook up with Finn.
Marceline = I think Marceline was supposed to be more of a challange for Finn and Jake, not a love intrest. Anyways, Marceline dosen't appear in alot of episodes anymore, so we cant learn much more aboout her past such in the episode "Memory of a memory", where we see Marceline with her ex, and her with her dad at the restraunt as her dad was eating her fries. Anyways, Marceline would never hook up with Finn.
