Grimace was spotted on the NYC purple line as Mets fans hoped for luck against the Phillies

Subway commuters got an amazing surprise.

Mets fans on the 7-line train before Tuesday's third NLDS game against the Philadelphia Phillies were greeted by Grimace – the team's Lucky Charm mascot, adopted by McDonald's.

The purple figure's face was also featured on the 10 cars of the train, which happened to be purple – including a sticker of Grimace wearing the iconic blue Mets cap.

The mascot boarded the train bound for Citi Field at the 34 St-Hudson Yards stop shortly before 1:30 p.m., the MTA said.

A hilarious video showed the purple giant bouncing in anticipation on the platform – as the doors opened to reveal a crowd of surprised Mets diehards.

The costumed monster jumped right into their arms and the group jumped up and down together with such ferocity that Grimace's head hit the roof of the train car repeatedly.

“Grimace! Grimace! Grimace!” shouted the crowd.

The costumed Mets fan enjoyed the rest of the 40-minute ride with the Metsies – before rushing into the stadium to watch the Mets play the Phillies in their third playoff game.

The trip is the latest in a strange and storied relationship between Grimace and the Mets that began in June when the fast food monster threw out the first pitch of the game.

“This celebratory moment was inspired by fans who socially photoshopped Grimace's face on the purple track after he threw the first pitch,” a McDonald's representative told The Post.

“They were unexpectedly joined by everyone’s favorite purple beast as she rode with fans to Citi Field to cheer on the Mets.”

Unfortunately, the stickers were a one-night special, even though the Mets will have at least one more game against the Phillies to have a shot at the World Series.

Tuesday's game is the first of the five-game NLDS series on the Mets' field, with each team entering with a single win.

The next two games take the NLDS to Queens for the first time since 2015, when the Mets split two home games against the Dodgers en route to the National League pennant.