Fans of 20-year-old pop sensation Billie Eilish were amused by her choice of guest singer during her Saturday night set at Coachella.

Eilish welcomed Blur frontman Damon Albarn onto the stage for a rendition of “Getting Older,” before moving on to “Feel Good Inc” by Albarn’s other band, Gorillaz.

However, when Albarn first appeared on stage, some of Eilish’s fans – many of whom are members of Generation Z – posted on social media that they didn’t recognize Albarn, 54.

“Who is that old man?” several people asked bluntly on Twitter.

“It’s so funny how none of us know who that old man is,” wrote one Eilish fan.

Some viewers mistakenly thought Albarn was Elton John, while others thought Albarn was Eilish’s father.

One user wrote, “We all thought the guy from Gorillaz was Billie Eilish’s dad lmaooo.”

“I’m glad Billie recognized him, because my guesses were the same as chat’s: Sir Elder Bieber John/Father?” Billie’s another person wrote.

Someone else wrote, “For a second, I assumed Damon Albarn was Billie Eilish’s dad.”

Others, on the other hand, were outraged, with one fan posting on Facebook, “How can some people not know who Damon Albarn is?”