The point of Mr. Blue was to say “What do you want her to do? Suck your dick?”, then die.
You mean, “What’s special, take you in the back and suck your dick”. He also is in it becuase he says the beautiful line “how many dicks was that”. There really was no need for him to be in it, there were too many people. It was a five man job, so i guess having him in there is a factual error. However, i liked him in it and thought it only helped the movie, not hurt it.