I was a Teenage Frankenstein has been on my "i need to watch that someday" list for a while.
The only actual I was a Teenage movie I have seen is I was a Teenage Zombie. It's not a good movie.
I love the box art though.
Also, by pure coincidence I once found a T-shirt that said "I was a Teenage Zombie" in glow in the dark letters at a goodwill. I used to wear that all the time.