Pretend You Love To Party Day!
Just write all over yourself with a magic marker. Then in the gym locker room, when a total stranger asks if you love to party, say "Check this shit out." Take off all of your clothes to show him all the embarrassing curse words and insults written all over you. The total stranger will say, "But that's all written backwards. You wrote that yourself in a mirror didn't you?"
You got served. Just change back into your street clothes and leave. When you get home, cancel your gym membership. It's guaranteed that that guy just told the entire gym about what just happened, and if you ever set foot in that gym again they're all going to point and they're all going to laugh.
Happy Pretend You Love To Party Day!