Frankie Muniz Jokes That Bryan Cranston Showed Up on Day One of Malcolm in the Middle Wearing ‘a Little Speedo’ (Exclusive).Linh

Although Frankie Muniz admits that “when [Malcolm in the Middle] was on, I never watched it,” he tells PEOPLE that he looks back fondly on his experiences with the “amazing friends” and “pen pals for life” he made while filming the hit series, particularly with TV dad Bryan Cranston.

The actor, 38 — who is teaming up with Spirit Airlines in honor of his “experience … being in the middle” and to promote their new #NotInTheMiddle “Go Comfy” Travel Option — says that his real-life experiences as Malcolm on the show have remained near and dear to him throughout his life.

Muniz fondly recalls his earliest memories alongside Cranston, who played his father, Hal, on the series.

“Bryan has been always such an incredible human,” he says of their relationship, adding that his former costar has “almost become like a father figure to me, I spent probably more time with my fake family on TV than I did with my real family when we were filming.”

In fact, Muniz recalls that Cranston’s now-timeless role in the series came to be just hours before filming began on the pilot.

“We hadn’t met Bryan because they didn’t cast Bryan, or whoever was going to play [his character], until a few hours before we started filming,” he shares. “And the first scene we filmed is from the pilot where my mom is shaving him in the kitchen while we’re eating breakfast.”

“And so Bryan Cranston comes in wearing a little Speedo, you know what I mean? And he’s like, ‘Hey, I’m going to be your dad,’ ” Muniz jokingly recalls, adding that it was “just a memory that just sticks with you … because that was the beginning of moment that really changed my life as far as the show.”

Those familial tendencies and memorable moments extended to Muniz’s experiences with his other castmates as well.

“You end up doing seven years, 151 episodes with this other family and it’s just pretty cool,” he says. “We had so many fun memories together and fun times together. Like me and the boys really kind of became like brothers. We played together, we’d bicker together, we’d fight each other. We really felt like that … not sibling rivalry, but you have that sibling relationship. Because we were spending 12 hours a day with each other for seven years, you can’t help but be close.”