Goof: Erica told Monica and Ross that she was going to finish packing. However, seconds later Joey and Chandler were packing in the guest room, since Monica and Chandler were moving out. However, the guest room belonged to Erica during her stay in the apartment.
Note: Ross asks Monica why Erica isn't staying with them and Monica says she put Erica up in a hotel because they're moving in a few days. In other words, Erica was never in the guest room.