I'll second "The Girl in My Life." Also, the promos for "That's My Line," hosted by Barker and done in 33, made it hard to believe it wouldn't be a game show.
But the one that stands out to me (although not quite on topic) was the old game show that turned out to be a new one. When what was then CBN began airing "Jackpot!" in the afternoons, TV Guide used the same description used in 1974 when the show premiered (including the reference to $50,000), so I was elated that I'd finally get to see the show, as the Atlanta affiliate didn't carry the show back then. Imagine my disappointment when that was not the case.