Sean emailed me this plush toys description:
"I was wondering if you could help me identify a stuffed animal I used to have in the very early 90s. It may have been older as my grandmother did have an awful habit of regifting unwanted toys to me. It was a blue bunny rabbit, but I'm sure they came in other animals and colours. Anyway, the unique thing about this toy was its stomach. It came with a plastic heart that was held on it's stomach by a small piece of velcro. You would put this heart into the freezer and when it got cold you would rub it on the bunny's stomach to make it change colours. When the toy heated up again, the stomach would go back to it's original colour. I loved this toy dearly as a child, but my mother tossed it when we lost the heart to it. Lo and behold, my mother found the plastic heart in her freezer a few years ago and my search for the bunny began. The heart has been in there for over fifteen years now and the writing is almost all scratched off so it offers no clue to the identity of my lost bunny. I just cannot find any mention of this toy anywhere and no one else remembers the name either, just the stuffed animal. Any idea the name of this long forgotten toy? Thanks for the help."
Sean
Andrea and Amber emailed me these two images and further descriptions:

"I also have a similar stuffed animal, a polar bear whose belly turns blue when gets cold by the crystal. It does not have a name on the tag, only 1993 Mattel."
Andrea
"I can't remember what it was called (I think there was "Crystal" in the name.. but not sure.) Maybe the photo will help though! Hope it helps!"
Amber
UPDATE!!!Thanks to Sean herself, Zuse and Holly who all identified the bear as an
IceTickle Bear, produced by Mattel in 1994. I can't find mention of the bunny line, but image it was called an IceTickle Bunny.
If you know anymore about the bunny line, or if there were more than three bears made please email me!
Go to my IceTickle Bears & Bunnies page!http://www.ghostofthedoll.co.uk/Toys_IceTickle.htm