Fans have been taking to Twitter to celebrate Paul Rudd on his 52nd birthday, even if most of them just can't believe he's actually that old. Looking virtually the same now as he did starring in Clueless over 25 years ago, Rudd's apparent inability to age has led some to wonder if he may in fact be a vampire. In any case, the man is now supposedly 52 years old, and fans everywhere are praising the Ant-Man star on his special day.

Leading the charge is Rudd's Avengers: Endgame co-star Mark Ruffalo, who posted an image of Rudd wearing the Infinity Gauntlet. Thinking he may have solved the mystery, Ruffalo writes: "Happy birthday, Paul Rudd! Did I find the secret behind your eternal youth?"

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A Tommy Doyle fan account based on Rudd's character in Halloween 6: The Curse of Michael Myers posted two images of the actor and tweeted, "Happy 52nd birthday to Paul Rudd. I still wish he was in Halloween Kills."

"Omg it's paul rudd's 27th birthday everyone cheer," another tweet reads alongside a couple of images of Rudd. If you didn't know he was really 52, it'd be pretty easy to believe he had just turned 27.

Another fan posts side-by-side photos of Rudd in 1997 and 2020, adding in the caption: "...and this is how you age when you're unproblematic."

"happy birthday to this man who ages like a fine wine. happy birthday, paul rudd," says someone else.

And Elizabeth Banks, who co-starred with Rudd in Role Models, posted a picture of herself and Paul with a tweet that reads: "Happy birthday to my forever favorite on-screen boyfriend/brother (it's not weird)"

The perception that Rudd cannot physically age is not lost on the actor. During a Clueless cast reunion in 2019, he was asked about his anti-aging secret, and Rudd joked that he's "80 years old on the inside. In here, pure darkness - and a little moisturizer."

Along with his memorable roles in 90s movies like Clueless and Romeo + Juliet, Rudd is also acclaimed for his roles in various hit comedies like Anchorman and The 40-Year-Old Virgin. He is probably best known for playing Scott Lang in the Marvel Cinematic Universe, which includes starring in his own solo movie Ant-Man and its sequel Ant-Man and the Wasp. He'll be back in the role once again for the upcoming sequel Ant-Man and the Wasp: Quantumania in 2022.

Rudd can next be seen in the movie Ghostbusters: Afterlife when it is released this year. The movie serves as a direct sequel to the first two Ghostbusters movies and will feature Rudd as an original character new to the franchise. Rudd can also be seen in the official trailer playing a teacher who's apparently obsessed with the classic Ghostbusters team from the 1980s. Following multiple release date delays, the sequel is currently scheduled to be released in theaters on Nov. 11, 2021.

Given that it's Rudd's birthday, it wouldn't be a bad time to watch one or two of his movies to celebrate the day. Let us also take the opportunity to wish a very happy 52nd birthday to Paul Rudd!