I had always assumed that hyenas were related to dogs, and if not in Canidae, at least in a closely related family. They look like dogs to me. Nooo, I find that their family, Hyaenidae, is more closely related to meerkats and mongooses (Herpestidae)!
I hate it when I find out stuff like this. Granted I’m happy to clear up my own misconceptions, but I don’t like having such misconceptions. It’s much like when I first discovered that Malta exists. I was ~14 at the time, and my thoughts were, “HTF did I not notice a country sitting smack in the middle of the Mediteranean! I stare at maps all the time!”