In the case of the Doctor Who revival, part of the reason the Dalek didn't show up until late in season one was that it was unclear they'd get the rights to use the Daleks from Terry Nation's estate until production had started on the season. They even had a backup version of the script in which the Dalek was replaced by a one-shot monster; the working title was "Absence of the Daleks".

I was tickled that they started with the Autons, because the Autons were the only Doctor Who monsters ever to actually scare me in childhood. The first time I ever saw the show on PBS, it was one of the Pertwee Auton serials, and I found the idea of mannequins with guns hidden in their hands too disturbing to go back and watch that Doctor Who thing again for quite some time.

Since the first serial broadcast in America was "Spearhead from Space", it's quite possible that I was freaked out by the very first appearance of Doctor Who on American TV.