No worries, I've done some research and concluded this is normal toddler behavior.
A couple of months ago, I bought Snuggles a pair of Crocs. In case you're not familiar with them, Crocs are a type of slip-on shoe made out of some combination of plastic and rubber. They are lightweight and washable. They're pretty much the perfect shoe for children. Anyway, a couple of months ago, I bought a pair of navy-colored Crocs for Snuggles. He immediately fell in love with them, which was cute at first. But now, Snuggles is absolutely addicted to his Crocs.
Snuggles doesn't care whether or not his Crocs match his clothes. He wears them anyway. He wears them to church. He wears them in the sandbox. He wants to sleep with his Crocs on. He wants to wear them in the bathtub. He literally screams when we take the Crocs off his feet. Of course, I don't give in to the screaming. I just tell him "I know you like your shoes, but we don't wear shoes in bed," and then brace myself for the screaming to ensue... which I promptly ignore.
In the past, the first Snuggles did when he woke in the morning was ask for his milk. I'll give you one guess what Snuggles asks for now when he wakes up in the morning... "I shoes!" (Toddler Translation: I want my shoes!)
Tuesday evening, Snuggles played in his sandbox and kiddie pool in our backyard. We were out of swim diapers, so I left him in his regular diaper, which quickly disintegrated in the water. So I took it off. But Snuggles didn't mind...
He still had his Crocs on!