I encountered this creature a couple of times while playing Super Mario Galaxy, but could never get close to it:
So far, I haven't been able to find any information in any walkthroughs, and I'm not sure what it's called, so my searches have come up blank.
Is it possible to catch this creature?
If it is possible, what happens when you do catch it?
Best Answer
Oh, this is a fun little guy. He is, in fact, an enemy, so yes, he is interact-able. If you manage to chase this bugger down (running long jumps help here) and spin/stomp him, he will explode in a shower of ~20 star bits.
They're called "Starbags" according to Super Mario Wiki.