But of late, Mewes has played the enigmatic Jimmy the janitor in comedy-horror series Todd and the Book of Pure Evil - think Buffy meets Peter Jackson's Braindead and you're pretty close!
While in London for the recent Jay and Silent Bob Get Old live tour - a spinoff from the popular podcasts - Jason spoke to Digital Spy about his new role and the future of Jay and Bob...
How have you been finding London?
"It's been awesome. We've been here five days - lot of sight seeing, a little shopping. We love it here! Kevin and his family's going to be here - his daughter's going to be here and she's going to wanna do some sight seeing, so hopefully we'll get to go back on the London Eye again! It's been sweet."
How did you get involved with Todd and the Book of Pure Evil?
"Through a friend - we worked on Degrassi and kept in touch. He also worked on Zack and Miri Make a Porno. Todd was a short first, and before it became a TV show, we were talking about doing a web series. When he told me about the scripts, I thought it was an awesome idea and told him that I'd love to be part of it.
"He was partners at one point with the producers of it, and told them how much I liked it. We were trying to make it as a web-series or something, and when they finally got it going as a TV show on SPACE in Canada, they said, 'Hey, d'you still want to be involved? We'd love you to be part of it'."
So was your character Jimmy written for you?
"Somewhat. After they knew it was me [playing it], they wrote it a little bit towards me. They had the character in there already, but they sort of fine-tuned it for me to do it."
Who is Jimmy and how does he relate to Todd (Alex House)?
"He's the janitor, but he's more than a janitor. As the seasons go on, you get a little more background on who Jimmy is and why he's at the school. At first, he's sort of the mentor - the Yoda - to Todd, and later on you learn more and more about why he gives him advice and what he's teaching him for.
"As it goes on, you do learn more backstory and why he's taken a liking to Todd, more so than the other kid he hangs out with. So yeah, there's something about him. He's Yoda!"
Do you know if a third season of Todd is in the works?
"I don't know. I know that they've written some scripts [for season three] and I'm just waiting to hear - hopefully we'll hear soon what's going to happen. I'm hoping!"
You're here in London for the Jay and Silent Bob tour - are you excited to bring the show to the UK?
"I am, I'm definitely excited. We put it on sale here and it sold out in a week or something. I didn't realise how many people would want to watch the podcast live here. It's exciting for me because it'll be the first time I've performed here.
"Kevin's done his An Evening with... and his Q&As - I was here with him a couple times and jumped on stage for like a minute, but that was his show and I was just part of it. But this is our show. And it's a huge theatre, so that's exciting - it's one of the bigger theatres we're going to be performing at."
Were you aware that you and Kevin had such a strong UK following?
"I didn't. I mean, I'd been at his Q&As and they've always been big, but I didn't realise. It's like, 3,200 seats at the theatre? London's 3,200, Edinburgh's 1,800... so 5,000 [total]. I had no idea, so it's very exciting. I knew we had a few fans here, but I had no idea that we'd sell out 5,000 seats in, like, ten days or something. I'm psyched."
Do you have much interaction with fans on the street?
"Not here. We've walked around, but of course we're bundled up - it's a little chillier for us! I don't get recognised that much. I've had a few people come up and wanna take some pictures and stuff. But it's interesting here, they're very reserved. They haven't asked me to scream out any lines or anything!
"But it's been very nice. I had a couple the other day and they told me, 'There's no way we thought you'd be out here' because they don't know about the show or whatever. But they're like, 'Are you that guy...?'. So it's been here and there, but nothing crazy."
We last saw Jay and Silent Bob on the big screen in 2006's Clerks II - do you think we will see those characters again?
"We've been working on a Jay and Silent Bob animated movie, so that will be on the big screen. But live-action? I'm not sure yet. We'll see. Kevin's next movie is Hit Somebody so that's gonna take some time to shoot, and post-production and all that. When that's done, we'll see how he feels.
"I mean, he said after Jay and Silent Bob Strike Back that there'd never be another Jay and Bob movie, and then we shot Clerks II - so we'll see. It's up to Kevin really, but I'm not against it."
What's coming up for you next?
"I believe Kevin wrote something for me in Hit Somebody, [there'll be] some more touring with Jay and Silent Bob Get Old and I have a few movies that are in post-production and will hopefully be out in theatres and on DVD. And hopefully season three of Todd!"
Todd and the Book of Pure Evil premieres in the UK on Syfy on Tuesday, March 6. The Jay and Silent Bob Get Old podcasts are now available to download for free.