Obama improvised the viral size joke about Trump at the DNC, his speechwriter says

• Barack Obama made a suggestive hand gesture while mocking Donald Trump at the DNC on Tuesday.
• The size joke was a hit with the audience and with many people online.
• Obama's speechwriter said Obama improvised the visual gag on the spot.

Barack Obama's viral joke about GOP nominee Donald Trump at the Democratic National Convention on Tuesday was improvised on the spot, says his speechwriter.

The former president dunked on Trump's "weird obsession with crowd sizes" during his speech while drawing his hands together to demonstrate that he was referring to a small size.

The visual gag drew laughs from the audience and led some people online to speculate that Obama was cracking a different kind of size joke at Trump's expense.

"Just so you all know, that was just in the moment," Jon Favreau, Obama's former director of speechwriting at the White House, said on the latest episode of his podcast "Pod Save America," which aired Wednesday.

The "dick joke," Favreau said, was written by Dan Pfeiffer, Obama's former communications director. But the suggestive hand gesture was all Obama's, Favreau added.

"He just put his hands on the podium," Favreau said on the podcast.

While the joke was a hit at the DNC, it infuriated Trump, who saw it as a personal attack.

"He was taking shots at your president, and so was Michelle. You know they always say, 'Sir, please stick to policy. Don't get personal.' And yet they're getting personal all night long," Trump said of Obama's speech at a rally in North Carolina on Wednesday.

When asked about Obama's remarks, a spokesperson for the Trump campaign told Business Insider the Democrats were launching "unfounded personal attacks" because they "don't have any real solutions for the problems everyday Americans face."

"This is why Kamala and Democrats will lose in November — they're more interested in personal grievances than in helping people," the spokesperson added.

To be sure, Trump is no stranger to mocking his political opponents with nicknames and personal attacks.

The GOP nominee made fun of President Joe Biden's age by calling him " Sleepy Joe " and has been testing out multiple nicknames for the new Democratic nominee, Vice President Kamala Harris .

"People say, 'Sir, don't do it.' You know all my names. They've all worked, they've all been very successful," Trump told rallygoers on Wednesday.