Though one of the only actors to appear in all three franchise installments, Breaking Bad's Mike Ehrmantraut was only created because one key actor wasn't available. Introduced in season 2 of the beloved AMC crime drama, Mike worked as a cleaner and hitman for the Salamanca cartel, having first been dispatched by their attorney, Bob Odenkirk's Saul Goodman. Jonathan Banks would later reprise the role for the prequel spinoff, Better Call Saul, which expanded on his backstory as a former corrupt Philadelphia police officer who turned to the New Mexico criminal underworld to support his daughter-in-law and granddaughter.

During a recent appearance on The Rich Eisen Show, Rhea Seehorn reflected on her time in the Breaking Bad franchise following the conclusion of prequel series Better Call Saul.

The star recalled how one of her co-stars, Jonathan Banks, only came to be a part of the universe because Bob Odenkirk was not yet available to appear as Saul, thus leading to the creation of the cartel cleaner/hitman. See what Seehorn shared above and in the quotes below:

Bob was not available for Saul Goodman to clean up her body, and so the Mike Ehrmantraut character was created. [Bob] was shooting something, and they wrote, when Krysten's character dies, that he comes and cleans up the body in this very cold, unfeeling manner. And that was going to be where his character started to go, and he was simply not available, so they made up the Mike Ehrmantraut character.

Related: All The Characters Mike Killed In Breaking Bad & Better Call Saul

Why Mike Was So Vital To Breaking Bad's Success

Aaron Paul Jonathan Banks

Though he may have been an afterthought for the franchise, Mike was ultimately a major key in Breaking Bad's long-standing success. Initially introduced as an antagonist to Aaron Paul's Jesse and Bryan Cranston's Walt, the series saw him evolve in his various dealings with the drug-amaking duo, namely as his bond continued to grow with the former character, even if it was in the hopes of driving a wedge between the two. But still, Mike having to spend time with Jesse granted audiences the first glimpse at his vulnerability and let them care about the antagonist for the first time.

Mike's death in Breaking Bad season 5 proved to be one of the most heartbreaking for many audiences, making his cameo appearance in the opening moments of El Camino: A Breaking Bad Movie all the more emotional. By further exploring his backstory in Better Call Saul, the emapthetic connection audiences had with Mike grew tenfold, as they learned how his days as a corrupt cop led to his son's death and the deep depression he endured after. Unlike Giancarlo Esposito's Gus Fring, who remained villainous even as his backstory became clear, Mike has become considered an antihero much like Saul and Walt.

Interestingly, Mike's belated creation in Breaking Bad wasn't the only major development made by Vince Gilligan and his team after the fact. Better Call Saul initially didn't plan for Michael McKean's Chuck to become a major villain for Odenkirk's Jimmy in the early seasons, with Seehorn recently revealing this was changed thanks to the star's complex performance as the character's brother. With both McKean and Banks earning Emmy nominations for their performances, they proved last-minute changes can be just as effective as pre-planned ones.

More: Mike Now Has THREE Perfect Breaking Bad EndingsSource: The Rich Eisen Show