"Hey, aren't you ..." Well, no. As famous as they are, celebrities sometimes get misidentified as another A-list face, but many told The Associated Press that they take it in stride.
"I get (mistaken for) everyone, anyone who has red hair," laughed "Mad Men" star Christina Hendricks, who has been confused with Oscar nominee Jessica Chastain.
The culprits include a department store worker who wrongly identified her as the "Zero Dark Thirty" actress.
"Chastain's epic," Hendricks said.
For Chastain, the redhead double take usually involves Bryce Dallas Howard : "I remember one time being on the subway and I was looking at a magazine and there was a picture of her in it, like a small picture, and I was like 'What am I doing in this magazine?' I actually had that thought," Chastain recalled.
Even Howard's dad — director Ron Howard — was once fooled, Chastain said. "I was walking by and I was like 'Oh, that's Ron Howard.' And then my friend who was with me said he turned to someone and goes 'I think I just saw Bryce.'"
When the 2011 film "The Help" came along and the two actresses got to work together, they ran to a mirror. "We looked at each other, at our faces, and we were like 'Yeah we look exactly alike,'" Chastain said.
It's not just about the redheads.
Sienna Miller is often mistaken for a certain fellow blonde: "Me and Naomi Watts are friends, but we often get sent each other's headshots to sign, which I'll take happily."
As for Watts, she gets mixed up with friend and fellow Australian Nicole Kidman, but she doesn't really see it. "We sometimes look at each other and go, 'It's not the nose, is it the lips? No it's not that. Is it the eyes?' I don't know what it is."
And it's not just women.
Jake Gyllenhaal , thinks it's just good hair in general.
"I think as actors we like to think that we're special, but most of the time people really can't differentiate any of us. We're all sort of the same, with no real special skill besides the fact that you know our hair looks nice 'cause somebody else did it."
If you mistake Samuel L. Jackson for another actor, don't expect him to correct you .
"I just sign what they want me to sign for whoever they think I am," he said. There's one actor he's consistently confused with: Laurence Fishburne.
Gabrielle Union said she gets mistaken for "every black person you've ever met in life, famous or not."
Among her supposed lookalikes are singers Brandy and Ashanti and actresses Sanaa Lathan, Regina Hall and Halle Berry. Union blames the identity mix-ups on laziness.
"Last night I was walking out of a restaurant and the paparazzi was, he might have been the laziest paparazzi I've ever encountered. He was like 'Are you a singer?' I was like, 'Yes, I'm Ashanti.'"
Pakistani-American comedian Kumail Nanjiani cites Kunal Nayyar, Aziz Ansari and Hasan Minhaj as his celebrity lookalikes, and it works both ways.
"It happens to them with me," he said. "And so, I feel at least we all have this weird thing in common in that we get mistaken for each other, even though we don't really look alike."
In a more unusual identity goof, Mindy Kaling said she's been mistaken for Nobel Prize-winning activist Malala Yousafzai : "I was once mistaken at a New Yorker party for Malala. And I said, 'I'll take it. She's 19. That's fine.'"
When it comes to some British male celebs, "Dark Phoenix" stars Michael Fassbender and James McAvoy said they've both been mistaken for Ewan McGregor, while Michael Sheen has been mistaken for a host of other celebrities.
The latest is his "Good Omens" co-star David Tennant. "Someone thought that David was playing both parts as well."
On occasion, comparisons rise above gender. Who is "Game of Thrones" star Sophie Turner's famous doppelganger?
"I haven't got mistaken for them, but a lot of people say that I do look like Boy George," she said. "It's true. I see it too. I'll show you pictures. It's kind of crazy."