MLBN played a July 4, 1985 game between the Mets and Braves (sometimes known as "the Rick Camp game"). It lasted 19 innings and 6 hours/10 minutes. According to the box score, it started at 9:04 p.m. local time (because of a rain delay). There was a second delay during the game, and the outfield was soaked. A good chunk of the fans stuck around for the postgame fireworks, which actually got shot off around 4:00 in the morning! The Mets took a 7-4 lead in the top of the 8th, only to give up 4 runs to the Braves in the bottom of the 8th. The Mets tied the game in the top of the 9th and held the Braves in the bottom to force extra innings. Each team scored 2 runs in the 13th inning. The Mets scored in the 18th inning. The Braves had no remaining pinch hitters, so they had to let relief pitcher Rick Camp bat with two outs in the bottom of the inning. With an 0-2 count, he lined a ball over the leftfield wall to tie the game. Camp then proceeded to allow 5 runs in the top of the 19th inning. The Braves scored 2 in the bottom of the inning before finally losing.
The game featured a player who had made his major league debut in 1963 (Rusty Staub) and at least one player who played into the 21st Century (Dwight Gooden). Gooden had started the game but pitched poorly and was removed in the third inning. According to Bob Costas and Tom Verducci, who provided commentary between innings, Gooden had apparently gone back to the team hotel and fallen asleep. He woke up at some point with the TV still on the game. At that point, he thought it was highlights and went back to sleep.
It was more enjoyable to watch than I expected because they edited out most of the time between pitches and also skipped the scoreless extra innings.