LOL, my dorm when I was an undergrad outlawed carnivorous fish and any pet that wasn't a fish. I had a figure-eight puffer who ate snails. Little carnivore. Like anyone inspecting would've known by looking at the fish that he was a carnivore. I also had a panther gecko and a guinea pig stashed under the bed!
I'm also a big fan of cories, but you need to keep more than one of them to keep them happy. I'm not sure if a 5 gallon would work for that. Partly I think, it depends on what type of 5 gallon you have. Mine is a hexagon- taller than it is long, which is bad for the cories, who are bottom dwellers. They might be okay in one of the shorter, longer 5g tanks, but I really don't know... I think they need more room. They're always on the bottom and they're pretty active. Usually at least a 10g is recommended for them.
An African Dwarf Frog might be an idea, too. They swim more than walk. lol They can live alone, although I've heard that they're more fun in pairs. I've never had one, but I think that they can do fine in a 5 gallon.
Oh, and is your tank cycled, or do you do frequent 100% water changes? Some fish (most fish) need to be introduced to fully cycled tanks. I know that cories are included in that number; not sure about the frogs. But depending on the type of fish you decide to add, it's good to know whether they need to be in an established tank if yours isn't. You may need to cycle it.