Supporters of Vice President Kamala Harris and former President Donald J. Trump responded online to the presidential debate on Tuesday with a torrent of jokey memes, video reels and surreal, computer-generated art that reached a whole new level of strange.

The alternate universes playing out of who won the night is the first time that online legions for Mr. Trump and Ms. Harris are going toe to toe.

Even in the hours before the debate, Mr. Trump’s son Donald Trump Jr., Republican elected officials and others shared digitally generated images of cats and ducks gathered in support of the former president. Mr. Trump shared an image of cats wearing Make America Great Again hats and holding assault rifles, and another of himself on a jet surrounded by cats and ducks.

Those posts came after Mr. Trump’s campaign and his running mate, Senator JD Vance of Ohio, acknowledged on Tuesday that a false and outlandish claim that Haitian immigrants in Springfield, Ohio, were abducting and eating their neighbors’ pets, which Mr. Vance had amplified, could be false. Mr. Vance nonetheless encouraged his supporters to continue spreading the rumor.

After the debate, Mr. Trump’s supporters painted him as heroic and victorious. Paul Ingrassia, who describes himself as “Writer of President Trump’s favorite Substack” on his LinkedIn profile, shared a computer-generated image of Mr. Trump emerging with a lion from its den.

Supporters of Ms. Harris, collectively known as the KHive, responded with memes and posts of their own. Some of those shared by progressives online mocked Mr. Trump’s response to a debate question about his policy plans — “I have concepts of a plan,” he had said — and depicted him as an old man grumbling about “eating the dogs” and “eating the cats.”

Another genre of online mockery poked fun at Mr. Trump’s claim that Ms. Harris “wants to do transgender operations on illegal aliens that are in prison.” A range of posts circulated images of extraterrestrial beings, including fictional characters like E.T. and ALF, dressed in women’s clothing.

In 2019, as Ms. Harris was preparing for her first presidential campaign, she told the A.C.L.U. that she supported “ensuring that federal prisoners and detainees are able to obtain medically necessary care for gender transition, including surgical care,” but the stance is not part of the platform on immigration that she released this week.

Chris Cameron and Ken Bensinger contributed reporting.