I posted this while on interminable hold for the emergancy vet on call. The vet said to watch him the rest of the weekend. She said that as long as nothing else happens and he seems fine, just call on Monday and bring him in so they can run some tests to pin point what caused it. But, if it happens again call her and bring him in. She said it unusual for cats to have a grande mal seizure, but as long as he's eating normal and his activity doesn't change he should be fine and bring him in Monday.

I'm still a little shaken. That so freaked me out. And he's walking around now like nothing happenned.