When Monica asks Pheobe about having sex in a public bathroom, she says that Chandler won't do that, yet they had sex in the bathroom at Central Perk when they were still just sneaking around.
The adoption agency would never allow a letter of recommendation supposedly written by a child to be officially be placed inside the applicant's file because the letter of recommendation is considered an official document and can be presented in court.
When Chandler and Monica look at Joey's recommendation letter and the letter becomes visible over their shoulders, it is obvious that the text is not even real words, but just a collection of @ symbols.
Ross enters Central Perk. He finds his friends plus, Amy and Emma. Ross is heard saying, "Hi Emma," but his lips don't match the audio greeting.
When Ross pulls off Emma's hat in Central Perk, he looks to Chandler, Monica and Rachel and mouths the words "what?" But no sound. He looks back at Emma and then back to the three on the couch and repeats "what?" Again but this time with sound right before he realizes Emma's ears are pierced.
Monica says that she proposed to Chandler. But she was too emotional, so Chandler did the actual proposing.
Monica claims that Chandler refuses to have sex in a bathroom, but in "The One After the Super bowl", Chandler was going to have sex with Susie Moss in the men's bathroom of a restaurant.