Images of the pair, who co-star in the new Netflix romantic comedy Your Place or Mine, went viral earlier this week, with many highlighting that they looked uncomfortable standing next to each other.
It turns out that Bad Moms actor Mila Kunis, who has been married to Kutcher since 2016, also thinks so.
Witherspoon spoke about the photos on US show Today on Monday (6 February), telling hosts Hoda Kotb and Jenna Bush Hager that Kunis “emailed” the pair after seeing the images online.
“She goes, ‘You guys look so awkward on the red carpet together’,” Witherspoon revealed.
In a separate interview, Kutcher revealed that it was Kunis that alerted him to the fact that the photos had been given the “meme” treatment.
“I did not see it,” he said of the response Chicks in the Office podcast, while comedically rolling his eyes.
He added: “My wife called me. She texted Reese and I together and said, ‘Guys, you gotta, like... act like you like each other’.
The actor suggested he was in a lose-lose situation as the media would have reported that he was “having an affair” with Witherspoon if they looked like they got on really well.
“Here’s the thing: if I put my arm around her, and was like all friendly with her, I’d be having an affair with her. Like, the rumour would be that I’m having an affair with her,” he said.
“If I stand next to her and put my hands in my pockets, so there’s no chance that that could be the rumour, the rumour is we don’t like each other.”
He continued: “Reese and I are really good friends, we’re really close. I don’t have to defend that,” he said.
The actor went on to give a reasoning behind why he looked awkward in the photos. He said that, as he’s “hard of hearing”, he finds promotional photocalls, which involves photographers noisily asking actors to look their way, to be an overwhelming experience.
“I can’t hear very well, ‘cause i’m hard of hearing in on ear and can only hear out of the other, I don’t know who’s calling my name, but I know there’s a lot of people yelling, ‘Reese! Ashton! Over here!’
“If you’re gonna tell me, in that entire 20-minute period, at one point you’re not gonna have an awkward face on, then you’re better than I am and I’m cool with that.”
Kutcher previously opened up about feeling angry with his ex-wife Demi Moore after she published personal details about their time together in a 2015 memoir.
Your Place or Mine will be available to stream on Netflix from 10 February.