Kel Mitchell Claims Dan Schneider Once Yelled 'Wild Stuff' at Him In a Closet

Kel Mitchell says he butted heads with Dan Schneider on their Nickelodeon show, and things reached a head when Dan allegedly took him into a tight space and unloaded on him.

The former Nick star recalled this alleged tense moment with Dan on Keke Palmer's podcast Wednesday. Kel says he didn't like Dan's writing and vision for "All That" and things got so heated one day, he claims Dan ordered him into a closet.

Kel goes on to describe what Dan allegedly told him ... and according to KM, it was all sorts of nasty things -- most of which he says DS was screaming.

Of course, Kel's account follows more serious allegations against Dan in 'Quiet on Set,' where he and other adults are hit with accusations of misconduct, including writing inappropriate jokes for minors ... as well as sexual harassment. Dan's denied those claims.

KM says he was 18 or 19 years old when his alleged heated exchange with Dan happened ... and instead of physically fighting, he says he decided to walk away and leave the show.

Kel says the show's "vibe" was changing under Dan -- and he didn't like how his character was being written ... leading to a big disagreement on set.

As we know, other ex-child stars claim they've gone through worse during their Nickelodeon days. Still ... it's not a great look for Dan, who's addressed a fair amount of this before, acknowledging some of the material he wrote back then was inappropriate, etc.

Of course, he's also suing the 'Quiet on Set' producers for defamation, claiming they painted him to be a predator, which he says is total BS. So, while he's expressed remorse over certain things during his reign ... he's also pushing back on how he's been characterized.