Dave, a student at a university seems to be getting a lot of sexual attention from women

Day after day, Dave seems to be with a different girl. His professor, Mike, comes up and asks him what his secret is. "Before sex, i bang my dick on my bedside table which numbs it and makes me last longer" He says. "Wow! And that works?" Mike asks. "Every time" Dave replies. So later that day, while his wife was in the shower, Mike bangs his dick on his bedside table and before he walks into his bathroom, he hears his wife. "Dave, is that you?"