Joey punches the wall that hasn't been spackled, and he makes a huge hole, but in the next scene the hole is gone and the wall is perfectly fine.
At the beginning of the show, when Phoebe sits down, she starts to take off her jacket. But a couple of seconds later, she has the jacket fully on and then takes it off again a few seconds later.
Danny's apartment layout completely changes from previous episodes(S5 E6 The one with the Yeti). When Monica and Rachel fog him there is a wall directly behind him when he answers the door to them, apologising. In this episode the wall has gone and the door leads straight into the living room.
Towards the end, Joey claimed to have written the five pages for a play for that day. However, the guys were only holding two pages of stapled paper. Based on how much they read and flipped, the pages were basically empty, even for a play script.
When Phoebe inspects the coins in the hand of donor, she verbally rejects a Canadian coin, but then she appears to toss that very coin into the donation "bucket".
After Phoebe says she's going to 'do the whole city', Rachel is heard laughing loudly, but shown sitting completely still with her mouth closed.
When Chandler enters the room to convince Joey and Ross of going to an ice hockey game, a microphone is visible on the top of the left side of the screen.
The guy looking for change for the bus calls Phoebe 'Blondie' but her hair is completely hidden under her hat and therefore the colour of it is not visible. In subsequent shots her hair is shown down from her hat and pushed back.