According to most casinos' rules regarding slot machines, when the "lurker" played the quarter and Phoebe pulled the lever resulting in the jackpot, Phoebe should have gotten the jackpot because she pulled the lever, which placed the wager.
When Monica and Chandler are at the craps table and are rolling the dice, there is a guy to Chandler's left with a yellow shirt with a pattern on it who appears to be mouthing Monica and Chandler's lines.
The little boy who laughs at Rachel's mustache is A.J. Foster. Since it was his first time on a set, Kevin Bright hired his real life parents to walk behind him in the scene. After, Bright was so thrilled with his performance that he took AJ into the gift shop on the set and told him he could have anything he wanted. AJ chose a squirting slot machine toy.
The Lurker is same the older lady that Phoebe shoos away from the donation pot in "The One with the Inappropriate Sister"
Thomas Lennon, the man who is Joey's hand twin, would later go on to star with Matthew Perry in a remake of The Odd Couple (2015) and 17 Again (2009).