10 Hilarious Comic Mistakes You Won't Believe Were Published
7. Professor Xavier's Name Drop - X-Men #17
Early comics clearly didn't intend for Professor X to be considered as smart as he is now, as X-Men #17 saw Xavier simultaneously warn Hank McCoy to not take off his mask and reveal his identity... while referring to him by name, completely ruining his secret identity.
Justifiably, it's not the world's worst mistake - but the fact that these two sentences are said literally one after another makes it unavoidable to spot, and thus incredibly difficult to not think about for the rest of the issue.
To be fair, with the first twenty or so issues of the X-Men the pressure must have been really on to produce comics as quickly as possible in order to see if they'd do well, so the reason slightly clunky dialogue like this exists is readily apparent. However, that doesn't stop it making the Professor look like the world's biggest hypocrite of all time.