These adorable bats are very, very popular among all the people I give my origami to. I fold them regularly, because I know people will always be happy to have one – I think it’s partly because of the magic of pop-ups, but they’re also particularly beautiful.
The bat on the right is folded with 24cm double-sided paper. The bat in the middle is from Tuttle Rainbow patterns 15cm. I don’t remember the leftmost paper.
You can find the (beautifully hand-drawned) diagram in “Origami Pop-Ups to Amuse and Amaze” (ISBN 978-1494299026). He also made a youtube video.