While Monica and Joey are talking and people in the background are coming to the cooking class, the cooking class teacher arrives twice.
When Ross and Rachel are at the till in the baby store, Rachel can be seen sniffing the contents of a bottle while Ross is talking to Katie. She then screws the lid on, but on the close-up, she is screwing the lid on again, despite already doing it.
Despite the fact that in the previous episode Rachel received a Diaper Genie on her baby shower, Rachel and Ross bought another one - among all the stuff they bought we can see the unpacked box with Diaper Genie standing next to the couch.
Monica pretends to be a total beginner at cooking ("I had to ask people what it's called when the water makes those little bubbles!") - but minutes earlier she confidently answered the teacher's question about the difference between hollandaise and bearnaise sauce.
A microphone is visible above Rachel right after she says: "Hey, you're back from your date!"
The store clerk tells Ross that he's like Indiana Jones, because he's a paleontologist who works out. Indiana Jones is an archaeologist, not a paleontologist.