Billionaire Elon Musk made a striking farewell to Donald Trump during an unusual Oval Office appearance on Friday. Sporting a black eye, Musk dismissed drug abuse allegations and pledged to remain a "friend and advisor" to the US president.

As the world’s richest man stepped down from his role as Trump’s chief cost-cutter, the Republican president praised Musk’s "incredible service" and presented him with a golden key to the White House.

But Trump insisted that Musk was "really not leaving" after four turbulent months during which Musk’s Department of Government Efficiency (DOGE) cut tens of thousands of jobs, closed entire agencies, and drastically reduced foreign aid.

"He’s going to be back and forth," Trump said, praising Musk’s efforts as the "most sweeping and consequential government reform program in generations."

Musk, who wore a black T-shirt emblazoned with the word "Dogefather" and a matching black DOGE baseball cap, acknowledged that the $1 trillion savings he promised would take time to materialize.

"I look forward to continuing to be a friend and advisor to the president," he said.

Yet much of the attention focused on the large black bruise around Musk’s right eye.

Speculation about how he got the injury grew stronger after the New York Times reported that Musk had used so much ketamine during the 2024 campaign trail that he developed bladder problems.

The SpaceX and Tesla CEO blamed the injury on his son.

"I was just horsing around with lil' X, and I said, 'go ahead punch me in the face,'" the 53-year-old said. "And he did. Turns out even a five-year-old punching you in the face actually is..." Musk trailed off.

When asked about the drug allegations, Musk avoided answering directly.

The New York Times claimed Musk, the largest donor to Trump’s 2024 campaign, also took ecstasy and psychoactive mushrooms and traveled with a pill box last year.

Musk struck back at the paper instead.

"Is that the same publication that got a Pulitzer Prize for false reporting on the Russiagate?" he said, referring to allegations that Trump’s 2016 campaign colluded with Moscow.

"Let's move on. Okay. Next question."

Later, when a reporter asked Trump if he was "aware of Elon Musk's regular drug use," the president replied, "I wasn't."

"I think Elon is a fantastic guy," he added.

The White House downplayed the report.

"The drugs that we're concerned about are the drugs running across the southern border" from Mexico, said Trump’s Deputy Chief of Staff Stephen Miller, whose wife works for Musk.

Musk has admitted previously to taking ketamine, saying he was prescribed it for a "negative frame of mind" and suggested the drug helped his work.

The farewell marked the latest in a series of highly publicized Oval Office events designed to put a positive spin on Musk’s departure.

Musk is leaving the administration amid frustration with his role and criticism of Trump’s spending plans.

This was a far cry from his early days as Trump’s chainsaw-wielding sidekick.

At one point Musk was nearly inseparable from Trump, accompanying him on Air Force One, Marine One, in the White House, and at Trump’s Mar-a-Lago resort.

Under Musk’s leadership, DOGE conducted an ideologically driven purge of the federal government, with young "tech bros" cutting tens of thousands of jobs.

But the agency’s results fell short of Musk’s original goal to save $2 trillion.

The White House claims DOGE saved $170 billion so far. However, the independent Doge Tracker site counted only $12 billion, and Atlantic magazine estimated savings at just $2 billion.

Musk’s "move fast and break things" approach also clashed with some cabinet members. Earlier this week, Musk said he was "disappointed" by Trump’s planned mega tax and spending bill because it undermined DOGE’s cuts.

Meanwhile, Musk’s companies faced challenges.

Tesla shareholders urged him to return as sales fell and protests targeted the electric car maker. SpaceX also suffered a string of rocket failures.