"He asked for a '13', But they drew a '31'"
The tattoo of the number 13 has several different connotations.
In the tattoo world, it's the opposite of 'unlucky 13' and is a symbol of GOOD luck.
It's also the 13th letter of the alphabet and is used to represent "La Eme" or "the Mexican Mafia", a hard-core violent Mexican street gang. Some wannabees get it inked to act tough.
Being the 13th letter, other get it to symbolize that they smoke marijuana.