I met a Boss version of him once. I don't remember anything special though, I just killed it. Banana the Hutt doesn't, to my knowledge, have a guaranteed drop. You may have just gotten lucky. The Crab King is a NICE one, by the way. He always drops a Crown of Yellow, with random enchantments. The level he's on also has a type of Witchy, so I used one to farm Crowns of Yellow. It was awesome.