Pepito is Rat's sock puppet that reflects his own personality.
What he says/does
Pepito is violent and ill-tempered, making him beat up or even kill people for not agreeing with him or doing something stupid (kind of like Rat with the Mallet O' Understanding).
Victims of Pepito
Goat became a victim when he didn't share his spaghetti with Pepito, who broke the bowl and threw spaghetti all over Goat.
Winky was Pig's attempted Sock-Puppet to help Pepito, but Pepito killed him.