Timothée Chalamet Wears a Mustache and Disguise to Surprise Hugh Grant on “Tonight Show”

The 'Wonka' star also donned a 'Love Actually' cap to fly under the radar on Jimmy Fallon's late-night talk show

Timothée Chalamet tried to pull a fast one on Hugh Grant!

Chalamet, 27, surprised his Wonka costar, 63, during an appearance on The Tonight Show Tuesday, attempting to fly under the radar as an unidentified, mustached audience member.

After chatting with Grant for a few minutes, host Jimmy Fallon said he was “out of questions,” and consulted the crowd for ideas.

Enter Chalamet.

Wearing a fake mustache, Love Actually baseball cap and large leather jacket, the Dune star donned a deep voice to ask, “You’ve worked with some incredible actors in your career… I was just curious, where does Timothée Chalamet rank on that list?”

Related: 'Wonka' First Look! See a 'Mischievous' Timothée Chalamet, Orange Hugh Grant in New Origin Story (Exclusive)

In true Grant fashion, the Notting Hill star — who appeared to see through the Chalamet’s flimsy disguise — provided a sarcastic response.

“I’m assuming this is not part of the show that’s going to be broadcast, so I’ll tell you the truth. To be honest, I didn’t like him," he joked. "None of us did.”

"I don’t know what it is — it’s something weird about that whole French Timothée Chalamet,” he added, pronouncing his costar’s name with an exaggerated accent.

A stunned Chalamet could only repeat “for sure,” and tried not to laugh before ducking out. Though, he eventually popped back up onstage alongside Grant.

Related: All of the Actors Who Have Played Willy Wonka

Although their hilarious appearance on The Tonight Show would suggest otherwise, the leading men of Wonka are actually quite fond of each other.

Earlier this month, Grant told PEOPLE about his first impression of the Little Women star, admitting that he "was a bit nervous of him” on set.

"I don't like people who are too successful, and I thought his career had gone a bit too well," the actor joked. "But I did warm to him. He gave me good gossip."

Related: Hugh Grant Jokes About His Free Time: 'I'm Swamped in Children and Too Old for Them' (Exclusive)

While chatting with PEOPLE, Chalamet offered an equally sarcastic first impression of Grant. “Before I met Hugh, I thought he was wonderfully talented and handsome and very good-looking. Then after I met him, my impression crumbled,” he quipped.

“This broken bitter old man.” Grant joked back.

In Wonka, a musical prequel set before the events Roald Dahl's Charlie the Chocolate Factory, Chalamet portrays the budding candy-maker, who has run-ins with an Oompa Loompa (played by Grant).

Chalamet revealed to PEOPLE that, unfortunately, the Wonka castmates did not get to act side-by-side, because Grant delivered his motion-capture CGI performance off-camera.

According to the young star, he "didn't get the deluxe Hugh Grant experience.” Instead, he acted opposite a tennis ball for reference.

"But he was close by in a tent," he added.

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"I couldn't be on the set because I'm too big,” Grant said of portraying the 18-inch-tall character. “But I was in a tent just nearby with my helmet on with all the cameras. A highly complicated business."

Wonka is in theaters Dec. 15.

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