The first time you get a 50 or 100 combo an item star will shoot off and grant an extra item at the end of combat. (Max 2 items) Tentacles should be a 1 in 4 chance I think, but I don’t remember everything the jellies drop and they should all be the same rate.
Alternatively, you can also clear rainbow oyons until you get a drop (a flying star will appear). As long as you can stay alive, the fight will keep going, so you could just clear the board over and over without attacking ^^
Some actions refresh the combo timer by the way, like casting a spell!
