[@World Traveler][@Raddum]

There was an RP recently with a game in order to be allowed to join the roleplay. It involved some text hidden in the OOC which actually contained the character sheet. If I remember rightly it was colour hex was the same as the background. What the GM wanted was a mini challenge for the players, sort of something to both get them thinking and see what sort of problem solving skills they had. 

Why? 

Cause it was a murder mystery RP and the GM wanted players who were curious thinkers rather than action writers. 

Was it a good move... Who knows, but old DOS games had hidden puzzles to unlock the game and he was perhaps inspired by some of these designs. Personally, I wouldn't issue a challenge like that these days, but on one of my RPs did many many years ago to see whether people actually read the rules.