An online video has emerged, showing Red Hot Chili Peppers drummer Chad Smith yelling angrily at a fan, who said "Will Ferrell" to him during a concert.
The rocker, who has poked fun at how similar he and the Anchorman star look in the past, is performing at the Los Angeles Musicians Institute in the footage.
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Smith is talking to the crowd in between songs, when an audience member yells "Will Ferrell" at him - then the fireworks start.
"Shut up!" Smith angrily responds, in a style very similar to many of Ferrell's movie characters.
He then jumps up from his seat, hits some of his equipment over and storms off stage.
After the rest of the band get a chant going, Smith comes back on stage to confront his heckler.
"Why did you say that?" he asks. "I'm not Will Ferrell, you idiot!"
In a more relaxed manner, Smith continues to say he's "just f**king with" the audience member and thanks Ferrell for making him "f**king famous".
Ferrell and Smith performed together on The Tonight Show in 2014, and took part in a 2016 charity benefit concert together.