Caine's Arcade Kid -- No More Cardboard Boxes ... Signs With HUGE Agency

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.