In a video released by MeidasTouch.com, which can be viewed below, Casler said the "DiaperDon" hashtag -- which has been trending on Twitter -- is not just a joke. In fact, he claimed, it is "based in reality."
"He would often soil himself on The Apprentice set," he said of Trump, speculating that the commander-in-chief is "incontinent" from all the mind-altering substances he ingests on a daily basis.
"You know, all that stuff has a laxative, it has an effect on your bowels and his are uncontrollable. He's worn diapers since probably the '90s."Casler went on to say he saw this "firsthand" while working on The Celebrity Apprentice a decade ago, alleging that Trump's assistant Keith Schiller was in charge of changing the real estate mogul's diapers and making sure he does not embarrass himself in public.
"You've seen it happen while he's in office," he added, claiming Trump soiled himself on at least two occasions: once during a meeting with Turkish leader Recep Tayyip Erdogan and another time at a press conference with Democratic Sen. Dianne Feinstein of California.
Trump is sometimes "unaware" of what's happening, Casler alleged, so aides and members of his family have to intervene.
The president often soils his diapers "in a rage," he claimed.
"He'll start to freak out, you know. One time, there was the word 'arbitrage' on a cue card and he started screaming that the script department was setting him up... and he just freaked out and then very loudly evacuated his bowels and you could smell it," he said.
Casler added that Trump and his aides have desperately tried to hide this problem, but alleged the outlines of the diapers are visible in many videos available online.
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Casler reasserted his claims in a tweet, adding that diapers explain Trump's posture. The commander-in-chief, he said, moves awkwardly because he uses a plastic girdle.
The comedian has previously made similar allegations.
In a 2018 interview with People, Casler said Trump took Adderall while filming his reality show and claimed he was often inappropriate around young women. Comedian Kathy Griffin vouched for Casler's credibility and praised him for releasing this information to the public.
Actor Tom Arnold also spoke highly of Casler, saying that journalists should pay attention to what he is saying because he has evidence that his claims are true.