Paul Rudd’s ability to seemingly not age has long astounded fans.

And, on Saturday, the 49-year-old actor revealed his secret as he reunited with his Clueless costars Alicia Silverstone, Donald Faison and Breckin Meyer at the Chicago Comic & Entertainment Expo (C2E2).

When asked how he stays looking so young, the actor revealed he doesn’t feel as young as he looks.

“I’m 80 years old on the inside,” he joked.

His secret? “In here, pure darkness,” Rudd said while pointing to his chest. “And a little moisturizer.”

The Avengers: Endgame actor caught up with Silverstone, 42, Faison, 44, and Meyer, 44, to discuss the movie’s legacy and reminisce about their time on set in the panel, which was streamed on YouTube by SyFy Wire.

Their reunion included a sweet tribute to costar Brittany Murphy, who died as a result of pneumonia combined with anemia and “multiple drug intoxication” from prescription and over-the-counter medication in December 2009 at the age of 32.

“She was so incredibly talented,” said Meyer, who also worked with Murphy on King of the Hill and Uptown Girls. “Ridiculously talented. Like, you see [her in Clueless], and then you watch 8 Mile, and you’re like, ‘That’s the same person?’”

RELATED: Clueless Cast Reunites and Remembers Costar Brittany Murphy Nearly 10 Years After Her Death

Also during the panel, Silverstone, Rudd, Faison and Meyer revealed where they think their characters would be now.

Fiason, who played Murray, said that he hoped Cher (Silverstone) and Josh (Rudd) were still together.

That was fine by Rudd, though he recognized the pairing was a little creepy considering the two were step-siblings at one point. “‘You guys are still together … and you’re still kind of related?'” Rudd teased.

Later, the costars shared photos of their time together backstage on social media.

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“So much fun hanging out with these boys today,” wrote Silverstone, captioning a selfie also shared by Faison and Meyer. “They had me laughing so hard on our panel. Such a great day at #c2e2”

She also revealed that she had eaten dinner with Rudd on Friday night. “Such a sweet reunion last night at dinner with my pal #PaulRudd,” Silverstone said, captioning a pic of the two. “I love this guy! I mean he ordered vegan for both of us….. Swoon 🤗”