Marceline’s outfit is half that one punk from Return of the Living Dead, half Misfits from Jem.
BMO is just BMO with shades and a powerglove. It’s so bad.
Finn is half Mad MAx, half Kenshiro from Fist of the North Star.
Jake is just Jake with a Flock of Seagulls hairmorph.
P-Bubs uses Jem hair and a Captain EO-based outfit(just more colorful).