When Joey is telling Chandler that he'd bow out of a relationship, Chandler has one dart in each hand. When Chandler whips around and Joey ducks, the dart in his left hand is suddenly gone.
When Ross is teasing Monica about banging Ben's head, she has some chopsticks in her left hand. When Ross is spinning around, they change to Monica's right hand without her passing them over.
At the end of this episode when Chandler and Phoebe are singing "Endless Love" by Diana Ross and Lionel Richie, Chandler is holding a vinyl copy of the 1982 album "Lionel Richie." The song does not appear on this album until the 2003 re-release.
The Friends' Apartment is at the corner of Bedford and Grove in Greenwich Village. According to Google Maps, the distance between adjacent buildings is about 40 feet. To allow for room at one end to maneuver it and room at the other to reach into Ugly Naked Guy's apartment, the Giant Poking Device needs to be at least 50 feet long. There simply isn't enough room in the apartment to create such a device.
Ross mistakenly says "Homo sapien" instead of "Homo sapiens."
Before the gang pokes the ugly naked guy you can see his stomach moving up and down as he breaths because he was alive from the beginning, he was only sleeping.