Keseranpasaren are based on Kesaran-Pasaran from Eastern Japanese mythology.
The Black Keseranpasaran also found during Mystery Time appear to be the dark counterparts of these creatures.
It's Catalogue description reads:
"A downy creature that loves to eat makeup" Edit
Mr. Graves asks students to find it, describing it as having big eyes and a body that looks like fluff.
He explains it in his lesson saying:
"Keseranpasaran are said to bring good luck to their owners. You can raise one by... keeping it in a wooden box with holes in it and feeding it white makeup powder."
In order to catch them you must move far from them and wait until they descend to rush towards them and use the net.