Joe Sugg admits he was 'starstruck' the first time he saw Mila Kunis
Wonder Park sees Joe Sugg and Caspar Lee lend their voices to a pair of beavers. They tell Georgia Humphreys about working on an animation, the stigma attached to their career choice and holding their own with stars including Mila Kunis and Jennifer Garner
Since recording their parts for new animation Wonder Park, Joe Sugg and Caspar Lee have had lots of pinch-me moments.
The Paramount Pictures film, in which the YouTube stars voice two cheeky beavers named Cooper and Gus, tells the story of June, a wildly creative girl who has a vivid imagination and who dreams up a fantastical amusement park with incredible rides, populated by animal friends.
It has a stellar cast, including Jennifer Garner, Matthew Broderick and Mila Kunis.
"It is so surreal... my name is next to Mila Kunis's name on the film poster," exclaims 27-year-old Sugg, known for his YouTube channels ThatcherJoe, ThatcherJoeVlogs and ThatcherJoeGames.
"I'm a huge Mila Kunis fan."
The Wiltshire-born star, who was also runner-up on BBC's Strictly Come Dancing last year, elaborates excitedly. "I walked past her in a lift once in Los Angeles.
"Obviously she didn't say, 'That's Joe Sugg,' but I was like, 'That's Mila Kunis'. And then I was star-struck for the rest of the day.
"I don't normally get star-struck, either. There's just something about her - she's just brilliant."
Sugg and 24-year-old Lee, a British-South African who was born in London, have both been making videos for YouTube since 2011.
They've amassed loyal fans from all over the world. Sugg has just over eight million subscribers while Lee 7.5 million.
But neither could believe their luck when they got the call about Wonder Park.
"They were like, 'Look guys, it's Hollywood calling - they want you to play two beavers', and we were like, this is perfect!" Sugg recalls.
The pair, who used to be roommates, have filmed countless videos together for their respective channels, with a focus on humorous pranks and comedy skits.
They are just as outgoing as you would expect them to be, considering they share so much of their lives online.
It's fun listening to them bounce off each other, especially when they're on the topic of getting into character.
"We became beavers for the next few months of our lives," Lee, whose YouTube channel is simply called Caspar, says dryly.
"Well, at least I did... I was in beaver mode, just constantly. I started eating wood."
"Method acting..." quips Sugg. "You should see his apartment. Building his own dam in his room."
Energetic Lee is keen to continue with the beaver jokes, this time about how the preparation affected his, erm, indigestion.
"I guess it's healthier than constantly eating pizza, which I was doing before," he says.
"But yeah, wood... It just hurts whenever you go to the toilet."
"I didn't go that far," Sugg chimes in. "I'm the sort of person that can switch it on when they need to.
"I stayed very calm and reserved and when they said 'beaver' - boom! I became a beaver."
It's become more and more common for successful online influencers to branch out into other industries.
Take Sugg's sister, Zoe, who started posting to her Zoella YouTube channel in 2009.
"She has since started writing novels and has her own beauty line.
Meanwhile Tanya Burr, one of the first big British YouTubers, has recently made the move into acting.
Sugg and Lee themselves previously featured in a BBC film called Joe And Caspar Hit The Road, and The Spongebob Movie: Sponge Out Of Water.
And the blending of YouTube stars and conventional Hollywood roles is something they see happening more and more in the future.
"I think we're very lucky to do this," says Lee of their roles in Wonder Park. "Paramount were really cool and down with it.
"These were really suited characters for us and if people enjoy it, maybe there could be a spin-off. That's my goal, to have a beaver spin off..."
He adds, sincerely: "But, yeah, I think there's a lot of talent on YouTube - not to say we are those - but I think you'll see a lot of talent rise up and do things like this."
"You drive down Sunset Boulevard and there's always billboards with content creators on," Sugg adds enthusiastically. "There was a time when we didn't know how it would go down, but I think now it's much more accepted, which is great."
Sugg has experienced first-hand what it's like for people to question his celebrity status. His inclusion in the line-up for the sixteenth series of Strictly caused quite a stir.
"There are so many people that are like, 'I pay for the television licence, so I demand to know every single person that works on the show!' It's like, 'I'm really sorry, that's not how it works, you're not going to always know every single person on a show'. But the whole idea is you get to know them," he says.
"I knew there would be a very mixed reaction to me being on the show, but it was fine.
"It's all part of it, and I got to the final, so they obviously got to like me, which was great."
Lee takes the chance to stick up for his pal, pointing out Strictly is a show watched by different age groups.
"You'll find lots of members of the younger audience would have only known Joe," he suggests.
There is no denying the entertainment industry is a changing economy.
Even traditional film stars, such as Jack Black, Will Smith and The Rock, have their own YouTube channels now.
It would seem there is no stopping ambitious vloggers like this dynamic duo.
"We're very lucky to have started YouTube just because we wanted to do it for fun and then it's evolved into this," says Lee.
"If I told my 16-year-old self I'd be doing a press junket for a movie we're in, I wouldn't have believed it, so thank you to YouTube, I guess."
Wonder Park is in cinemas now