The Nanny says there are two "L" in "Rolex". That is incorrect. However, this is a joke meant to, once again, showcase that Fran is uneducated and that the joke is on her. (She comes from Queens and that is a recurring joke.) --- Adding... actually this is often done with KNOCKOFFS in NYC. Canal Street used to be notorious for knock off merchandise. Fran could have gotten all her watches/purses/whatever from Canal Street or similar places throughout her life.
The mugger just told Sheffield and his nanny that he's broke, they repossessed his car and that he basically has no money. In the same conversation, he offers to treat both of them to a Shakespeare festival. "It's on me", he adds. That made no sense.