Man I really hate when I'm trying to talk to someone in a dream and they're either straight up ignoring me or interrupting me in some way. I always feel so helpless, and trying to grab them usually doesn't work well either, like they're just tangible enough to feel them but not actually ever touch them.
And also, when something happens that should be impossible, like in this case a person being here when they shouldn't be able to, or some (unwritten) laws that everyone seems to suddenly abide by but won't tell me about.