Still in the coffee shop whilst Frank and Pheobe are talking (they are now sitting on the same sofa) the ashtray on the table suddenly disappears. Nobody has come over to remove it.
Pheobe and her father Frank Buffay are talking in the coffee shop. One second his coat is buttoned up, in the next shot his coat buttons are undone and you can see his jumper underneath. When he goes over to sit next to Pheobe, his coat is buttoned up again.
In the opening scene, Chandler takes picks up the timer from his right side and puts it down on his left. When he and Monica switch positions, the timer is back on the right.
Phoebe greets a mourner at her grandmother's funeral and gives her a pair of 3-D glasses, telling her that the Reverend will tell them when to put them on. However, after Phoebe meets her father, she says she has to focus on saying goodbye to her grandmother - she and the rest of the group immediately put on the glasses even though the Reverend hasn't told them to yet.
When Phoebe's father leaves the funeral and Phoebe says: "Oh my God", her line and her mouth movements are significantly mismatched.
During the scene where Phoebe is talking to Ursula about their grandmother, shots from the back of Phoebe sometimes show her speaking with no matching dialog. That scene also shows a shot of Ursula holding the door, yet the door is absent when the shot moves to her back.
Phoebe mentions several times in the series that Frank abandoned her family before she was born, but Frank says that he used to sing songs to her when she was a baby.
When Monica starts massaging Chandler's shoulders at the kitchen table after everyone tells her they hate her massages, Jennifer Aniston breaks character and is stifling a laugh behind Monica and Chandler.