That awkward moment when you were looking forward to taking an elective during the summer because you were able to since it didn't have any pre-req/co-req until the professor that's taking over decided that you do need a pre-req and now you can't take it because you're taking the pre-req course in the fall.
I'm still bitter about that. The entire month of July is totally free now and I need to keep myself busy so I don't end up lamenting over the loss of a lab course I was looking forward to taking. More hobbies and side classes?