Ross Geller's bachelor party is depicted in the Season 4 episode, "The One With The Worst Best Man Ever".
The party is prompted by Ross' engagement to Emily Waltham. It is organized by Joey Tribbiani, who is Ross' best man at the time.
It takes place in 1998 and and is held at Chandler and Joey's apartment.
Guests include Chandler Bing, Gunther, and Ross' paleontology colleagues from the Museum of Prehistoric History.
Entertainment includes a stripper, who sleeps with Joey after the party.
Joey has had t-shirts made for the guests, which say Ross Geller Bachelor Bash 1998 on the front and Best Man Joey Tribbiani on the back.
The morning after the party, Joey realizes that Ross' wedding ring for Emily has gone missing. He presumes the stripper stole it before leaving his apartment that morning. It later transpires that, actually, Joey and Chandler's pet duck swallowed the ring.