The actor/comedian -- best known as Goldberg the Goalie from the 'Ducks' trilogy -- hit up the House of Blues in Anaheim for country singer Niko Moon's tour.

Weiss & Moon are both former addicts, and we're told Moon wanted to highlight Weiss' recovery -- pointing to him as a "hometown hero" of sorts -- since the Anaheim Ducks, who actually got their name from the film series, play real close to the House of Blues.

BTW ... Niko's donating all the streaming proceeds of his new single "Better Days" to the Happy Cowboy Foundation -- a charity he founded committed to providing free therapy to those dealing with mental health issues and drug addiction.

Anyhoo, check out the vid ... Shaun's clearly lovin' the atmosphere handing Niko his own Goldberg jersey -- before the chanting began.

If you haven't seen 'MD' ... the players hype each other up before a match by quacking together -- saying "quack" over and over before a big game. Here, Weiss did the same to hype up the crowd ... and damn, did it work.

We're told Shaun and Niko also jettisoned a few signed jerseys for the fans in the crowd ... showing off their baseball skills by chucking the hockey jerseys off the stage.

This all serves as a bit of a celebration for SW too BTW ... the former child star recently reached four years of sobriety -- though some people didn't believe it.

Remember, people were recently worried he'd broken his sober streak, but Shaun told us he definitely hasn't relapsed ... and says he'd make sure to ask for help if he backslid.