The Ant-Man star has held on to his membership kit for more than 30 years
During an appearance on Late Show with David Letterman, Rudd, 46, proudly admitted to his three-decade membership in the Letterman fan club.
“About 30 years ago, when you first started the show, back when the [Kansas City] Royals were in the World Series, I joined the David Letterman fan club,” Rudd said.
The Ant-Man star confessed he doubted the authenticity of the club, which Letterman said they had to issue a cease-and-desist order against.
Rudd still enjoyed the perks of his membership, though: “What it included was a pin, a collapsible drinking cup, a sponge that – if you put in water – would grow, a back scratcher and a balloon,” he said.
The actor held on to his yellow pin, proudly wearing it during his appearance, as well as the expandable sponge.
“Finally, now, three-fourths of my life later, we should see what happens,” he joked, as they watched the lackluster sponge work its magic in a bowl of water.
Late Show with David Letterman airs weeknights (11:35 p.m. ET) on CBS.