In an interview with Yahoo Global News Anchor Katie Couric, actor Bryan Cranston touched on how John F. Kennedy would have handled the landmark civil rights bill, what he thinks of Obamacare and why he’s still smiling after finishing the “role of a lifetime.”

Cranston transitioned from playing meth-cooking mastermind Walter White to embodying the larger-than-life Lyndon B. Johnson on Broadway with the help of his “terrifying” face, he told Couric.

(Explore Katie Couric's interview with President Johnson's daughters on civil rights)

The actor said he’s able to portray the harder side of the nation’s 36th president on stage using a facial expression that scares little children. Both LBJ and Walter White — the “Breaking Bad” character that made Cranston famous — share a ferocity that the actor captures with his flashes of cutthroat forcefulness.

Cranston said he tested out and perfected the emotionless mug over the years, even scaring people in grocery stores and other public places.

“Mothers are grabbing children's hands and pulling them away, you know,” the actor recalled. “And I'm just pleasant, but the look itself is nasty.”

The three-hour Robert Schenkkan play "All the Way," in which Cranston stars, follows Johnson during the year after John F. Kennedy’s assassination, when he took over the White House and quickly began pushing the Civil Rights Act through to the dismay of the Southern “Dixiecrats” in his own party. As it turns out, playing the president who finally brought institutionalized segregation to an end using a mix of charm and steel is not such a leap from portraying a chemistry teacher who reinvents himself as a drug kingpin to provide for his family.

Cranston said he’s not in mourning over the end of his run as the star of “Breaking Bad,” which he called “the role of a lifetime.”

“Don't cry because it's over, smile because it happened,” he said of his attitude towards the AMC show’s end. “That’s really the way I felt, is that I was the lucky guy who got this role of a lifetime.”

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“And I was in that moment. I was enjoying the moments that we were embracing, not only the experience of telling that story, but the experience of the experience of telling the story,” he said.

To more closely resemble the president on stage in “All the Way,” Cranston wears earlobe extenders and shoe lifts — Johnson was 6 foot 4 and burly. LBJ was a lover of junk food — Fresca, Cracker Jack and candy bars — and had the paunch to prove it, Cranston says.

The actor says he lives like a “monk” while in New York City, spending his one day off a week in near silence and doing little but working and sleeping.

“I try to just to stay away from people,” he said.

He’s had time to consider his character’s legacy carefully. Cranston believes that if Kennedy had lived, the Civil Rights Act, which went into effect nearly 50 years ago, may not have passed at all.

“If President Kennedy was alive, and was able to push it through, it would have been a much, much more watered-down version,” Cranston said. “And the freedoms that were achieved in that one document would have taken who knows how much longer.”

The actor said he believes President Barack Obama is emulating Johnson, who was known for ramming through legislation he believed in, through his strategy of using executive action to get around an intractable Congress. Obama has used executive orders relatively infrequently compared with past presidents, but vowed in his State of the Union earlier this year to lean on them more if Congress does not cooperate with him.

“I personally believe his health care program is fantastic,” Cranston said. “Yes, there are problems. Anything worthwhile is going to go through a growing pains period. But this is his legacy, and I think it's a great one because I don't think that basic health care should be a privilege of the rich.”

“It should be a right to all,” Cranston continued before stopping himself. “Sounds like I'm running for office,” he joked. Couric teased that the White House would be calling shortly to hire him. Cranston laughed. “It's what I believe,” he said.