Probably the most famous cameo star of all time, considering how many of his films the great director made an appearance in. Hitchcock is pretty much the most recognisable director to have ever worked, to the extent that he branded his own physicality as part of his film-making (consider the silhouette) so his cameos weren't exactly hidden or unexpected (which is why he won't be appearing in the main body of this list).
But that didn't stop the film media of the world proclaiming that they had found a hidden Hitchcock cameo in North By Northwest, and one for which the director dragged up, no less. The conspiracy theory centres on the somewhat portly woman seen above, who bears no small resemblance to the director himself. But no matter how pleasant the idea, that isn't Alfred Hitchcock at all.
It is in fact renowned character actor Jesslyn Fax who had also appeared in Rear Window.
She does look a lot like Alf though, God help her.