Catnip perhaps?

[DismemberedDoll]

I've seen this quite a few times with only this one cat.
Is it because of the cat nip mouse?
Or what?

http://i371.photobucket.com/albums/oo152/DimplesSkyscraper/Uploaded%20by%20AKH/Screenshot.jpg

[lauratje86]

I think it's the catnip! My sim cats get that too sometimes :-D

[PuX- 80's]

The mouse is a catnip toy.
I don't know about the stars, though.

[novemberlove_SC]

Whenever a cat plays with the mouse toy, it causes them to become hyper and see those stars spinning around their head, they also run around crazily and roll on the floor :P

[jenny]

Its super-cute:P

[longdaysend]

and incredibly realistic (except for the visible stars of course) as my cat becomes hyper-cat: the super hero when she has catnip. which was funny before we got her de-clawed..now it's hilarious as she takes flying leaps at the wood posts in the living room and just slides to the bottom,lol.

the first time it happened to a simcat i thought something was wrong until i realized there was nip in the mouse toy :D