If I put a festive outfit on a pet, is it on forever, or can it be taken off and put on another pet?  

I've been hanging on to these things since we got them.

They are just like Rainbow Jars. If you put it on, you can always use a Gray Jar or another Rainbow Jar to remove / replace the skin, but you will not get the festive outfit back. Just like a Rainbow Jar is used up when used, so is the outfit.

Thanks for the info.