The Geller Cup appears in The One With The Football. We learn that when Monica and Ross were younger, their family held touch football games called the Geller Bowl. Monica and Ross were always captains and extremely competitive. Whoever won received a trophy called the Geller Cup, which is really just a troll doll nailed to a two by four (which Chandler points out in the episode). While Jack and Judy took Ross to the hospital, Monica swam into the lake and fished the trophy out. She never told Ross and the first time it came up was twelve years later at Thanksgiving 1996.