BRUNSON BET Instagram/@nyknicks
Jon Stewart's got a message for sports gamblers ... don't do it -- or don't lose, at least -- because it forced him to get decked out in Philadelphia Eagles gear, pissing off his hometown crowd in Madison Square Garden.
Jon was rocking Eagles green from head to toe -- even had a bucket lid -- Saturday night at MSG, where he was watching his Knicks take on the Lakers. Normally, Jon's a beloved Knicks faithful, but some boos rained down on him ... due to his wardrobe.
He can thank Knicks star Jalen Brunson for all this -- they bet on last month's Eagles-Giants game, and since the G-Men came up short, Jon had to pay up .