We have three cats and upon receiving this package, they immediately showed interest in these chirping fluffy creatures. However, after about 2 hours of some throwing, batting, flinging and chewing, one of the mice didn't stop chirping. And it chirped.... and it chirped and chirped and chirped. Our cats looked at us with that look of "Why? Why did you give us this torture device? Make it stop!"
We tried everything, but eventually my husband had to take the mouse apart and take the battery out. It seems that if this toy gets a strong "knock", the microchip inside goes crazy. So to sum up: if the toy works, the cats love it. If it malfunctions, it drives you nuts.