Bryan Cranston has revealed Erik Per Sullivan won't be joining the Malcolm in the Middle reboot because he studying for a master's degree at Harvard

During an appearance on the 'Fly on the Wall' podcast, Bryan explained: "I talked to Erik and I said: 'Hey, we got the show! It's gonna come back.'

"He goes: 'Oh, that's fantastic!' And I go: 'Yeah, so we're looking forward to having you back.' He goes: 'Oh, no, no, I don't want to do it. But it's fantastic that you are'."

He added of Erik's decision: "He's actually going to Harvard,. He's really, really smart, and I think he's getting his master's at Harvard right now. He said: 'Oh God, no, I haven't acted since I was nine or something. So I'm not into it'."

The role of Dewey has been recast with Caleb Ellsworth-Clark taking over from Erik.

Bryan went on to admit it's surreal to see his young co-stars grow up as they are now all around the same age he was when he started working on Malcolm in the Middle.

He addeD: "It's amazing how these boys - who were my boys on that show - are now around the same age I was when we first started. They've got children of their own."

The show originally ran from 2000 until 2006 and Bryan previously revealed he's relished the experience of playing Hal once again.

He told People: "Slipping back into that character of Hal for me was so rewarding - I missed him.

"It's been almost 20 years since we said goodbye. And he's a sweet, lovable man. He's really a lovable guy, and it was fun to see all my whole family back together. It was great."

He went on to explain how his on-screen costume has helped him to get back into character.

Bryan explained: "It's a short-sleeve shirt that Hal would wear, a patterned short-sleeve shirt that screams out he's not going anywhere."