It went down when Willie got a call from Manny's manager who told him he'd seen Gabriel's artwork ... and he was a HUGE fan.
He spread the word to Manny, who commissioned two pieces from Gabriel about a month ago -- one solo Manny shot ... and one with him and his son.
We're told it took Gabriel about a week to sketch and paint the artwork (speed runs in the family) but then he really turnt it up ... making each painting into a 3D image that "JUMPS" out of the frame.
Gabe did the job for free ... But since Manny signed each piece and gave one back to Gabriel, he now has a piece of memorabilia that could be worth thousands of dollars ... although we're told he plans to keep it.
FYI -- Both Gabe and Willie say they are squarely in Pac Man's corner ... so add another celeb to Manny's stable of supporters.