Scruffy was Frank's pet hamster featured in "WHAT NOT TO SAY IN PUBLIC" and "FILTHY COMPILATION" until he died of serious physical abuse. The said physical abuse was Frank putting him in a sock and bashing him against his furniture, as said in the caption below the picture.
Scruffy i love you

Filthy Frank telling scruffy he loves him, after putting him into a sock and beating the crap out of him.

Scruffy somehow appeared again in "100 ACCURRATE LIFE HACKS", where Frank smashed him again in another sock, which he claimed is a life hack if your pet is misbehaving.

Fake Frank later references Scruffy in the video "LOSER READS HATER COMMENTS 5", saying how he could beat the crap out of Caleb Nimirowski's hamster. Oh wait... it can't because it's dead.