Pete Davidson is a captain at the Pro Bowl Games in Vegas this weekend -- which is sort of a weird sight ... but not nearly as bizarre as the ink Amon-Ra St. Brown was rocking.

The Lions WR was front and center Sunday for the off-weekend just before the Super Bowl next week, and during an interview with Robert Griffin III ... he showed off what appeared a relatively fresh tattoo he had plastered on his arm ... a tat of Pete's face, no less.

There's some writing underneath the drawing of PD's mug too ... it says, "Pete #1" -- as in Pete's #1 fan. Unclear if it's real or not, but Pete was brought over to take a closer look.

He was clearly impressed and moved by the gesture -- apparently, Amon-Ra is a big fan -- but he also said what most everyone else was thinking ... hopefully, that thing comes off!

As for why Pete's there at all ... he's just one of a handful of celebs on the field to help spice things up. Snoop Dogg and other stars are there too, and everyone's just goofing around and hamming it up for the camera -- notable during Pete's Best Catch judging.

Naturally, there were jokes made about his dating resume, which includes a lot of high-profile women he's been with over the years. Good sport that he is, Pete leaned in.

At one point, RGIII even made a little crack about Pete's "game" off the field ... and the dude was appreciative of the compliment -- noting, he's just there to have a good time.