"The One With Ross' Inappropriate Song" is the seventh episode of the ninth season of Friends, which aired on November 14, 2002.
Joey earned too much money to keep hiding it, so Monica suggests investing in real estate, such as Richard's apartment for sale; Chandler accompanies him, and they find a videotape marked 'Monica.' After watching the tape, Monica tells Chandler that it isn't her (saying that the tape showed 'her' wearing cowboy boots, but says she has never wore them in her life.)
Phoebe has her first dinner with boyfriend Mike's classy parents, Theodore and Bitzy Hannigan, and some boring acquaintances, but despite a chance to seem classy and 'normal', she disappoints his parents. But Mike sides with her and saying that they are too boring and their guests, and even calls her 'the woman he loves.'
Ross is the first to make baby Emma laugh, but Rachel is disgusted to learn that he made her laugh by rapping 'Baby's Got Back' by Sir Mix-A-Lot; but learns that it is the only way to make her laugh. Near the end of the episode, the others catch them both rapping to Emma and dancing provocatively.