The Pennsylvania senator responded to a post on X from a BBC disinformation reporter who noted there was a “community of people online who regularly share images of John Fetterman to figure out whether he’s real or has been replaced by a body double”.
“Senator Guy Incognito (D-PA),” Mr Fetterman wrote alongside an image of the Homer Simpson doppelgänger of the same name.
Using doctored images and deceptively cropped screenshots, social media users on X, formerly Twitter, TikTok, Instagram and other sites have been spreading baseless claims that the 54-year-old uses a body double.
“It looks like John Fetterman no longer has tattoos on his forearms,” one wrote on X in a 14 September post.
“They sure are getting sloppy with these doubles.”
The images, which were edited to hide Mr Fetterman’s body ink, have gone viral after being amplified by right-wing internet personalities.
The posts claiming Mr Fetterman’s forearm tattoos had vanished were taken from a clip of him reacting to House Speaker Kevin McCarthy’s decision to launch an impeachment inquiry of Joe Biden.
“Oh my gosh, it’s devastating,” the first-term senator said in a mocking tone while raising his arms when asked about the inquiry.
Bogus online theories that Mr Fetterman was using stand-in reportedly started after he was hospitalised for clinical depression in March, according to an AFP fact check.
Mr Fetterman returned to Senate duties in April after a six-week inpatient stay at Walter Reed Hospital.
In recent days, Mr Fetterman has repeatedly mocked Republicans who have taken aim at his trademark attire of hoodies and shorts.
After Senate Majority Leader Chuck Schumer opted to get rid of the Senate dress code, Florida Governor Ron DeSantis accused Democrats of “dumbing down” Congress.
“I dress like he campaigns,” the Pennsylvania senator said in a post on X, ridiculing Mr DeSantis’ misfiring presidential campaign.
Mr Fetterman told The Independent this week that he was revelling in the partisan attacks.
“My favorite one was that I’m a revolting slob,” he said in an interview with The Independent’s Eric Garcia.
Mr Fetterman added that the Senate had mush more important matters to focus on than his appearance.
“It’s just strange why, you know, with everything and the issues that we should be dealing with right now, we’re worried about how I dress,” he said.