Me Too!
Replaced batteries in my magic mouse (kirkland AA from Costco). Went to use it a day or too later, no workie. Opened it up, and one of the batteries had exploded!! Cleaned it up, put 2 more in (Energizer this time). Mouse didn't work, and I was comtemplating who would point the blame at whom. After sitting for 2 days, just opened it up - the same battery exploded again!!
Guess I'll call it in, and get set up with a new one on Apple's dime!
Oh, and my keyboard batteries are now low - I'm scared! 😉