You're never too famous to fanboy out over your idols — just ask Keanu Reeves.

The Matrix Resurrections star participated in a fun round of "The Colbert Questionert" during his Wednesday appearance on The Late Show with Stephen Colbert, during which he revealed which two celebrities he has asked for their autographs.

The first? The Velvet Underground's Lou Reed, said Reeves, 57.

"But it wasn't for me — it was for a friend, and [Lou] was cool about it," he recalled of the late rocker. "It was [on] a little piece of paper, and it was [in] blue ink. … Yeah, it was good. It just said, 'Lou Reed.' "

"It would have been really disappointing if it didn't say 'Lou Reed,' " joked Stephen Colbert, to which his guest replied, "I know, but it could have said, 'All my best' or ... "

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The second celebrity Reeves approached for their John Hancock was none other than legendary comedian George Carlin, whom he appeared with in 1989's Bill & Ted's Excellent Adventure.

"I'm so jealous. I'm such a fan," said Colbert, 57. "And that was for you?"

"Yeah," said Reeves. "He wrote … I think it was, 'Dear Keanu, F--- you!' "

While the actor "always thought he just wrote that for me," he admitted, "then I met someone else who said that he wrote the same thing to them! Anyway, beautiful."