Originally created for an ARPG contest, I think they'd work very well as Pokemon!

Interrobab
Interrobabs are constantly in a state of outrage. When they're in a group, they're known as a Forum. They are only capable of showing either a '?!' or '!?' on their bodies. They attack by bouncing at their enemies, and poking them with their pointy tails.
When befriended, they are no less outraged, they're simply outraged on behalf of their new friend.

Expleteen
Expleteens are capable of displaying more emotions, though few are pleasant. They travel around in Forums, usually under the direction of a Cussifer. Highly territorial, they like to attack by headbutting their enemies with their horns, shocking them with unpleasant symbols, and, again, poking enemies with their tail. They can display any combination of symbols, including '!@#$%^&*-_=+'.
They make for fractious companions, and need someone with strong willpower to keep them in check. But they are excellent guards, and fiercely loyal.

Cussifer
An Expleteen evolves into a Cussifer once they've beaten a sufficient number of their own and rival Forums' members. They are intelligent enough to use actual words, usually cuss-words (shocker, I know) such as 'Poop', 'Heck', 'Darn', and 'Dangit'. They can communicate with folk using their tails, but they prefer to just smash people with them. Combined with sharp claws, and a Forum of angry Expleteens at their command, they are a formidable opponent.
Cussifers are definitely less of a pet and more of a partner when befriended. They demand respect, and return it only when convinced their partner is worthy.