When Rachel is watching the birthing video with Monica and Chandler, she lifts her hands to her face and the ring seen on her right ring finger is Jennifer Aniston's engagement ring from Brad Pitt
The dog appears to be a Nova Scotia Duck Tolling Retriever.
The Magna Doodle in this episode shows a drawing of a guy on a motorcycle.
The way Ross says Happy Valentines Day to Mona is an exact copy of how Janice says it in her high pitch voice to chandler in 'The one with the candy hearts' in Season 1, Episode 14.
Rachel suggested to have Nick at Nite be a channel she and Ross can watch at their apartment. Interestingly enough, this show started to air on Nick at Nite in 2011.