I think cories are the most fun fish you can have in a small tank. Currently I have 3 pandas in my 36, waiting for the LFS to get more to up the school to 6. Its hilarious watching them play their "cory games." Its like they have set meeting times, they'll all swim all over the tank, checking out the different plants, then all of a sudden all three will converge together for a minute at the bottom front like they are comparing notes, then off they go back to their own thing, lol, I recently added 3 black phantom tetras and they sometimes get confused and try and school with the male, must be the similiar coloring, and the cutest thing ever is when they "sleep" they do it in a dog pile.
Long time ago I had otos in a 20G they made such quick work of the algae problem they lived on wafers. but they were cute but not as cute as the cories, IMO.