Petey

Elizabeth "Petey Peterson" Cacklebird is an undead dire rat, and Schmoopy's "familiar" pet. She was introduced in Episode 2 in both the original series and the remake. Petey was assumed to be of male gender until Season 3, in which it was reveled that Petey was indeed a girl.

Before Unforgotten Realms
Before the events of Unforgotten Realms, Petey lived a life as Elizabeth Cacklebird, Champion of the Arena, until she was bested in battle by Eluamous Nailo, who went under the alias "Wigglytuff". After committing a Sin of the Unforgotten, Petey was killed, only to be revived by Schmoopy during the victory feast.

During Unforgotten Realms
Petey was picked up on the side of the road by Schmoopy after he had just killed off The Beggar, to which Mike responded that he wanted Petey as a pet, but kills a poor innocent beggar. Petey followed the group and didn't naturally do much at all, but is still regarded as an important staple of the team.

Powers and abilities
Petey appears to be a very fast character with an assumed DEX score upwards of 20, and the aspect of being both undead and dire adds a disease effect to all of her attacks, and she can also use the poisonous gasses as stand-alone abilities. Petey can also be thrown.

In the original series, Petey was able to use Pokemon moves such as Hyper Beam, much to the chagrin of Mike.