The song the friends are humming in the beginning of this episode is the theme to The Odd Couple (1970). Ross tries to continue with the I Dream of Jeannie (1965) theme when Chandler stops him.
The DVD version of the episode features a scene where Paolo spots Ugly Naked Guy, who is making shadow puppets.
This is the first episode to show Phoebe's occupation as a masseuse and Monica's competitive nature.
After Ross finds out about the sex of the baby, the girls rush over to give him a hug. As they do, the elusive closed closet door is slightly open revealing a neat closet.
In the opening sequence, the friends started humming the theme song to The Odd Couple (1970), with Ross starting then all the others joining in. Matthew Perry later starred in the new version of The Odd Couple (2015). Thomas Lennon (Joey's identical hand twin in Vegas several seasons later) is Matthew Perry's co-star, playing roommate Felix Unger.