Taylor Swift Slipped into Chiefs Game Unnoticed at Arrowhead Stadium

Here's something that almost NEVER happens to Taylor Swift ... walking anywhere, much less into an NFL game, with zero fanfare -- but we've learned that's exactly what she pulled off on Sunday.

This shot shows Taylor -- rocking the Chiefs' windbreaker -- walking into Arrowhead Stadium to see Travis Kelce and his team play the Chicago Bears. The woman in the black leather jacket is part of Travis' PR team, and she escorted Taylor and Trav's friends to his luxury suite.

The amazing part is ... we're told there were no fans screaming for Tay Tay as she walked into the stadium, and made her way to the suite.

You gotta hand it to Taylor and Travis for pulling off the perfect sneak attack. No one knew she was going to the game -- we got wind of it just 20 minutes before kickoff -- and, as a result, the Swiftie army was NOT lined up to see her arrival.

Kinda shocking they weren't on the lookout, considering Travis made it known he had invited her to a game.

As we reported, Traylor (yeah, that's what we're calling 'em) were quietly escorted out of the stadium -- and only one reporter, WGN's Jarrett Payton, was able to get a quick shot of them inside.

They pulled away from Arrowhead in a pretty conspicuous way, though -- looking like Danny and Sandy from "Grease" in Travis' metallic purple convertible muscle car -- but they definitely pulled off a 'Mission: Impossible' getting her in on the DL.