There aren't that many rules to engaging in a physical challenge. I do, however, believe that the first one is to make sure you are going to win. I'm not talking a friendly wager in the gym or during a practice. I'm taking about every day life. You can't just walk the streets, or theme parks, challenging every person that looks at you funny to a pushup contest. If you do, you better be damn sure you come out victorious. Safe to say that rule two is to not be inebriated during the encounter. I would be lying if I said I haven't indulged in a few adult beverages at Disney World, but then again, I also wasn't trying got take on Chip & Dale in a tag team match. Beer muscles are a legitimate phenomenon. A phenomenon that exists in bar fights against other drunk people. It also aids in the quick recovery from drunk battle wounds, until the next morning that is. A great example of this is when this kid shatters his chin attempting to do one arm pushups like a hero. Sure, he probably painted the town red shortly there after, but you can bet your ass he didn't feel the true brunt of his actions until the next morning. Regardless, no amount of beers is going to increase your physical abilities.
Like I said, you have to know your opponent. Especially if you are going to put your 'talents' on display in a public setting. One of the last people I am challenging to a push-up contest is a Disney character. I am not saying every Disney character is a picture of perfect health, although it does take some amount of endurance to prance around all day dressed in a costume in the Florida heat. If there is one thing I know about the people that are hired to play Disney characters it is that they are one firing away from sucking dick to pay rent. If there is two things I know about them it is that they are showmen. They are entertainers. Maybe not the most prolific of entertainers, but entertainers none the less. Never has a mascot or a person in a costume ever agreed to a challenge they weren't certain they would win, and never has a person in a suit been a good sportsman. If you happen to win you're the asshole that challenged Gaston to a pushup contest, and if you lose you are publicly shamed in from of a bunch of 5 year olds on leashes and their miserable parents. Just a no win scenario. Plus, if you go into a showdown with a man in a costume as the underdog, you are doing something very, very wrong.
BONUS: Possibly the best mascot showdown of all time...