The bizarre theory has swept the internet after eagle-eyed viewers analysed footage from last week’s inauguration parade.
As President Trump, his wife Melania and their son Barron walk down Pennsylvania Avenue they were surrounded by an army of Secret Service bodyguards.
One bodyguard has come in for particular attention due to the slightly unusual way he was holding his arms.
The bald agent’s eyes can be seen looking around attentively while maintaining close proximity to the First Family.
A bizarre conspiracy theory has developed over one of Donald Trump's bodyguards
While all this goes on, the agent’s arms never move from their fixed position.
One of the first people to notice the abnormality was a user on the blog Frag Hero.
They wrote: “After yesterday’s presidential inauguration, many members of the military and law enforcement community noticed something very unusual about one of Trump’s bodyguards.
“The conclusion they reached was that he did indeed have tactical fake arms.”
The poster went on to specify he believed the agent was carrying a sub-machine gun under his black coat.
However, others have moved to debunk the claims. Writing on the Task and Purpose website, Adam Linehan, who served in Afghanistan and Iraq, dismissed the speculation as something drawn up by people who play popular video game Call of Duty.
Mr Trump was sworn in as president on Friday before his parade in Washington D.C.
He wrote: “The bodyguard, In the background of the image, exits one of the vehicles in the motorcade, and adjusts his tie and coat the way a man – a human man with functional arms – does whenever he's about to appear in public.”
Get Quotes on Home Insurance
Mr Trump has continued with efforts to uphold some of his campaign pledges by moving to redirect federal funding towards a wall on the Mexico border and to restrict access to the US for refugees from certain countries.
The reported orders are expected to involve restricting access to the US for refugees and some visa holders from Iraq, Iran, Libya, Somalia, Sudan, Syria and Yemen, said the aides and experts, who asked not to be identified.
The executive order signing, expected to be made on Wednesday, comes after Trump pledged during his campaign for a “complete and total shutdown” of Muslims entering the US – a promise he has since scaled down.