"Bad Joke"

So this is a story our friend Shelby will never live down...If you know our friend Shelby, you are aware of how absolutely BLONDE she is. So we were in gym class one day and we had a substitute teacher. If you know me, you know I am the queen of racist jokes [though I am not racist, the jokes are just funny]. So we were sitting around telling racist jokes when our substitute teacher, Mr.Martinez, walks up to us and joins in on the fun. He told us some really good ones, and Shelby starts telling her joke in front of everyone, including Mr.Martinez, "What's sign language for Mexican?!", and she proceeds to do the motion [which is 2 legs 'hopping' over a fence]....Everyone at this point is dead silent, except for miss Blonde who is laughing her ass off...after about 10 of the longest seconds of my life, she realizes she told a Mexican joke in front of a Mexican teacher and then tries to play off like she didn't laugh and says "Man, you guys, racist joke are NOT funny!" I then try to salvage the situation by telling the best white joke I know...which is not very good...The teacher just stares at us, and walks away...oh the sh** my friends say [and do]