Henry Winkler is looking back at a “wild” moment in his life, thanks to a throwback video that a fan posted on Twitter.

In the video, Neil Diamond is performing in Los Angeles in 1977 when he invites Winkler onto the stage to join him for a duet on “Song Sung Blue”.

At the time, Winkler was television’s biggest star, thanks to his role as Arthur “The Fonz” Fonzarelli on “Happy Days”.

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That led Diamond to ask Winkler to sing the song “like The Fonz would do it. How would The Fonz sing this song?”

As a result, concertgoers witnessed the somewhat surreal spectacle of Winkler channeling Fonzie to sing Diamond’s hit.

Winkler commented on the post, explaining why he seemed to have some difficulties with the rest of the song after singing “Song sung blue, everybody knows one.”

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“This was wild because I did not know the lyrics,” Winkler tweeted, “but i was a tremendous fan.”