For a random event to do on the Strip, the Shark Reef Aquarium for a local is cheap and amusing. I got in for $13 with my Nevada ID, and my friend who's a local teacher got in for way less.
They give you a free audio wand and you can leisurely walk through this place even with a crowd, watching and listening to all the pre-recorded sessions. It was actually pretty good for an audio tour! Especially the part where it tells you that the loafing Komodo Dragon could, with a single bite, slowly infect and kill you with its bacteria-ridden mouth. Scary!
And of course the fish and the aquarium tanks looked really well-kept and amazing. Even the non-chalant jellyfish were illuminated well, the only sad part was the giant 16-foot octopus who was tucked in its corner cave. There were many sharks, naturally, and they were serious business!
It's a nice 30-40 minute exercise if you're near that side of the Strip, fun for the family or a couple bored twentysomethings!