You can wear it (one time only) and your Tama looks like a Panda (instead of a Black-faced Mimitchi). It is also worn for the whole day until the Tama falls asleep.
I always think it's funny to see how your Tama looks disguised as a Panda - and trying out all the items on your list - it is hilarious watching the Tama stomp across the screen in the Panda costume wearing the wellington boots...
sorry, tamamum, but you can keep it on as long as you want, only if you pause it before 10:00 pm, (keep it paused all night) and then unpause it after 10:00 am. that's how i keep the costume that looks like a sheep on.