Really good idea for feral cats or barn cats in a barn that is really cold.
I got this idea from:
By the way, I let the 2nd kitty out of the cage yesterday and she is sticking around. She's staying right by Pepsi and coming when I call for dinner.
Here the two of them are. Stuck right together!
The gray one is the mother of Pepsi.
Both spayed now of course.