Mirror gag pre-dates Marks Brothers' version!
I saw parts of this film last night on TCM. I was amazed that the classic Mirror gag (or Mirror Scene) actually pre-dates when the Marks Brothers did it in Duck Soup (1933).
For those of you that don't know: its where a person looks into what they think is a mirror, but its actually another person. They do that thing where they wave their hand in a circle and other things that are miraculously mimmicked perfectly by the other person. Easily the oldest visual gag ever. I've seen it in cartoons (Scooby Doo, Bugs Bunny), wrestling (Doink The Clown), I Love Lucy (Lucy with Harpo), etc.
What amazed me was how unfunny it was in 7 Years Bad Luck. The guy pretending to be his reflection was a few inches shorter, timing was a bit off, plus they were too close to each other and he touched his back a few times, but the guy still thought it was a mirror. Come on!
None-the-less I can see why people would find it funny 90 years ago. Elderly people would probably still find it funny 'til this day.
Celebrating 10 years on IMDB