Using the search function of 'adventure drop', this is what I came up with:
Circadian - Found: adventure drop during The Slumbering Princess event
Denise the Seahorse - Found: adventure drop during Under the Sea event
Gerard the Lobster - Found: adventure drop during Under the Sea event
Glimmergras Flamingo - Found: adventure drop during The Great Glimmergras Celebration event
Seyndia - Found: adventure drop during The Fast and Fluttering event
Thankful Turkey - Found: Adventure drop during Fowl Play for Dinner event
I'm sure there are others, but this was just a quick look...