This doesn’t show intelligence per se, but it is certainly curious behavior. Here’s Nora, the piano-playing cat:
What prompts animals to do things like this? I cannot believe it’s simply random. It’s certainly not instinctual. (I have friends who believe that all animal behavior is purely instinctive — a position I believe is completely indefensible if you spend any amount of time with animals.) I’d love to see research into this sort of animal behavior.