Folks got two World Series games in one as the Dodgers needed 18 innings to beat the Blue Jays ... but Jerry O'Connell wasn't gonna miss a single moment of action -- even though he REALLY had to take a dump.
The actor documented his entire Monday night at the ballpark on his social media page ... initially smiling from ear-to-ear as he made his way to Game 3 of the Fall Classic.
JOC was all-in on the experience ... even playfully jawing at visiting Jays fans in the crowd early in the contest.
Little did he know, the "Kangaroo Jack" star -- who is married to supermodel and actress Rebecca Romijn -- was in for a LONG night .