Face Cat is a cat who resembles Cat Face physically but his facial features consist of two real life eyes and mouth and nose of a Cat. His first appearance was in Episode 11 taking Cat Face's usual intro portion with his own intro song, after the intro Face Cat is shown floating around the kitchen facing around before Cat Face enters and shoves him back into a cat flap with a broom, Cat Face commenting on riff raff coming through after he opened the portal to Face Cat's own dimension.
Face Cat appears again in episode 17 in the background floating down the hall before leaving through the front door's cat flap, Cat Face urges him back inside and after an airbomb repeater starts Face Cat rushes inside whilst Cat Face hurries to help him afterwards he is sniffling and shaking with Cat Face giving him a lecture on the dangers of the worlds customs.
Since he has made a returning appearance it is likely he will appear in future episodes.