When Monica and Chandler are discussing whether to spend their savings on their wedding or their future, Monica says "you said cat but you meant dog right?" But it's a recurring theme throughout the show that Chandler is scared of dogs. However, it has not yet been established that Chandler is afraid of dogs, which until The One Where Chandler Doesn't Like Dogs (2000) the only other person who knows is Joey (who tells him "DON'T do it" just before Chandler reveals the secret). Monica believes Chandler is allergic to them until then, which was his lie so he could stay away from dogs, but we do not know when she found out about his "allergy" so it could have been after she asked if he meant dog instead of cat.
When Chandler and Monica are talking to her parents about the wedding and they tell her they spent the money, she asks, "What about when I started dating Chandler?" but when she firsts asks it, the audio doesn't match. Then it cuts to a new shot and the audio and visual match.
The entire series, Ross is referred to as a "medical marvel" because they never thought his mom would be able to conceive a child. In this episode, Monica's parents are out to dinner with her and Chandler when they tell the story of when they got married and how he had gotten Judy pregnant before the wedding, accidentally.
When Monica's parents tell her they used her wedding fund to buy a beach house, then used what they saved when Monica dated Richard to redo the kitchen, Monica asks what about when she started dating Chandler. Monica and Chandler hid their relationship from everyone when they started dating. They had their one year anniversary in Vegas, then moved in together when they came back to NYC. Monica's parents' didn't find out till The One Where Ross Got High and Ross tells them at Thanksgiving dinner. Monica's parents would have had very little time to start saving once they learned about the relationship to when Monica and Chandler became engaged, even if they had started to save.
When Joey goes to take a nap in Rachel's bed, he pulls back the bed spread and exclaims "Pillowcases!" as though they are a complete novelty. Joey, in fact, has pillowcases on his pillows and they are satin.