It’s a magical Jedi crunchy frog! He Force teleports out of Jabba’s stomach each time he’s eaten. 😛
I assume that some slave, possibly a Jawa on stilts, has the job of keeping Jabba’s crunchy-frog bowl topped up at all times from a supply cupboard/pond out the back.
Actually because of the way that scene is edited, as a kid I thought that Oolah had somehow been shrunk by some machine beneath the trap door and transported to that bowl, and Jabba was then eating her. But that’s a discussion for the “childhood misconceptions” thread.
Almost sounds like something you’d find in the Phantasm series.