The adorable kid from the Caine's Arcade viral video -- who couldn't afford arcade games and had to settle for cardboard boxes -- is about to start raking it in. We found out he just inked a deal with one of the biggest talent agencies in Hollywood!

According to legal docs filed in L.A. Superior Court -- and obtained by TMZ -- 10-year-old Caine Monroy was signed by William Morris Endeavor. Caine is now part of WME's client list which includes Denzel Washington, Ben Stiller, Tina Fey, and Steve Carell -- so it's a pretty big deal.

And to think it all started after a video of Caine went viral last year --  featuring the East L.A. child ingeniously using cardboard boxes and trash to build himself an arcade in his dad's used auto parts shop.

Hollywood ... sometimes good things happen here.

The cardboard-cutting days are over for that kid from the viral 'Caine's Arcade' video -- because TMZ has learned, he's finally getting a real-life arcade game ... worth upwards of $4,000.

In case you haven't seen the video (below) -- a 9-year-old kid named Caine Monroy built an entire arcade at his dad's L.A. auto shop last summer ... using nothing but cardboard left over from his dad's stockroom.


Nearly a million people have seen the video in the last two days -- including the owner of an L.A. pinball shop ... who then invited Caine to come check out her store ... and even meet a bunch of pro pinballers, including world champ Keith Elwin.

Sources tell TMZ, Caine showed up to the store last night -- a place called Pins and Needles, where he played on a real-life pinball machine for the first time in his life.

But the fun didn't end there -- we're told Caine made such a strong impression on the store's owner (above) ... she offered him one of several pinball machines ... ON THE HOUSE.


The vintage machines range in value -- starting around a couple hundred bucks -- but the mack daddy is the rare "Big Brave" machine (above left) ... worth an estimated $3,000.

Caine has yet to decide which non-cardboard machine to take home.