I can think of two times this happened to me...
1. When I was a kid, I saw a listing for a show on USA in TV Guide that read "It's Your Move". That's it, no mention of the genre or anything. However, I took a guess and thought it was a game show off of the title. With my knowledge of short-lived TV shows being infinitesimal at that time, imagine my disappointment when I watched and saw that it was a sitcom. I wasn't upset for long when I learned, "Wow, I never knew David Hogan & Steve Rhodes did a show together". I stuck it out for the cast and it ended up liking it; it was a fun show. Coincidentally, the episode I saw was the one where the two of them go on a game show!
2. In the late '90s, I was surprised to see this listing on my local Fox affiliate at 3:00AM:
THREE'S A CROWD--Game
Intrigued, I set my VCR to see if they got the rerun rights to the game show or if it was a typo. I checked the tape the next day and sure enough, it was the latter (It was the short-lived Three's Company spinoff with John Ritter).