A smallish exhibit of critters at the Mirage. It's a nice break from all the drinking and debauchery going on. I've been a couple of times and I enjoy it, but it is small and at $22 a ticket, it isn't cheap. I probably wouldn't go unless I could find a discounted ticket (we had a BOGO from MyVegas).
There are about 5 big cats who have been sleeping every time I've been. They're adorable and awe inspiring but they don't really do much. The dolphins are of course cute as can be, but I've just become so uncomfortable with the idea of these creatures living in these tiny pools... I've gone all "Blackfish" about it, I know. Anyway, there are so many kids/families that have purchased the premium packages (FEED the dolphins, KISS the dolphins, TOUCH the dolphins, WTF?) that you won't get to see much of the dolphins as they're busy with the more high paying customers.
Still, if you can get yourself a deal and are doing the full on tourist Vegas thing, this is a good stop that should take about an hour or so.