>>40315370Fur Coat
Doesn't make any sense thematically but going from 60 Defense to 120 Defense is a pretty decent buff considering how slow it is already.
Prankster would also be decent, but it really wouldn't live long compared to other Prankster users and it's stats want it to be an attacker instead. Just a very bad one.
Maybe just make an entirely new ability for it that just automatically uses a status effect, like gravity or trick room or magic room. Or hell, if you really wanna go far out there, you could give it a completely new unique and insane ability, like letting it move twice in one turn instead of the usual one, or do something similar to speed boost except it's the opposite and affects both defense stats every turn. But that's treading into dangerous territory and I don't think I'd want abilities like that in Pokemon just because GameFreak never seems to be able to keep exclusive moves and abilities to Pokemon and they eventually go into others.
Utilizing Magic/Trick/Wonder Room would at least give it a niche though, especially in Doubles.