If you press Y and N at the same time, you will select both options and two people will come in next, one will leave and one won't.
Y and N at the same time when there is a yes/no decision.
It's a feature! You're now playing in a quantum reality! jk, that's crazy, I can hardly believe I never found that one myself. Good find, I will have it fixed in the next update :)
Some side effects are, you can also skip creatures, the bar at the end of the day that says how much happiness you have earned/lost in the passed day has gone, creatures will appear at the end of the day, when you get some people at the end of the day, you can get double and you get both of the stuff from the creature. For example, when the blob asks you to tell people to stop calling him slimeball and you do this glitch, you will get 3 happiness and lose 3 happiness!