bf and pibby were just wondering through a grey and white void when they stumbled upon finn Mertens!?...but he was corrupted by that strange glitchy substance that turns cartoon characters into mindless zombies

Bf: pull outs Finns "finn" sword from "is that you?" episode

Pibby: clenched her fists ready to fight!

the corrupted finn approaches them with his regular sword "scarlet"...he was smiling Menacingly while the static goo still on him bf and pibby need to have caution...