PS premiered "The Court Jester" at Sundance, and he went full Simmons for the role -- he looks a ton like him with the hair, tank top and thigh-high shorts ... and on top of that, Shore picked a viral moment from Richard's life. While the screening took place during the festival it was not an official Sundance selection.

The short -- not the full-scale biopic he's making -- opens with a production assistant backstage of a show hosted by a woman who looks and sounds like Ellen DeGeneres ... when Richard is called onto the stage.

Pauly's Richard comes out with a ton of energy, running around in front of the audience, sweat dripping down his forehead ... a clear reenactment of Richard's appearance on "Ellen" more than a decade ago.

Check it out ... Richard jumps around so fast cameras can barely keep up, pushes the same DVD and even pretends to be a workout machine Ellen can use -- art imitating life taken to the extreme!!!

Pauly's also showing off his acting chops in the more low-key moments too -- having a heart-to-heart with the PA from the beginning of the short while chowing down on a sprinkle donut.

Shore's clearly trying to be pretty respectful of Richard ... backing him with an angelic light while he drops knowledge on the young "Ellen" crew member -- though at this point, Richard's probably not coming around to Pauly's upcoming biopic

As we reported ... Richard -- who doesn't speak publicly much anymore -- came out and blasted Pauly's movie ... basically saying he didn't give his permission or blessing to Shore's project.

When we talked to Pauly about it ... he said he's holding out hope Richard comes around, but he's going forward with the project whether he gets the fitness guru's thumbs up or not.