Mark Harmon Made His TV Debut in a Kellogg's Cereal Commercial with His Father, NFL Player Tom Harmon

He revealed that although the experience "changed [his] direction," it was still "humiliating" for his teenage self

Mark Harmon wasn't originally too fond of his acting debut.

The actor, 73, recently joined Kelly Ripa and Mark Consuelos for Live with Kelly and Mark in Palm Springs on Wednesday, Nov. 13. During their conversation, he told the daytime talk show hosts that his first role was actually beside his father, football and broadcasting icon Tom Harmon.

The NCIS star explained that his father was a Kellogg’s spokesperson and he was asked to join him in a commercial for one of its products, specifically Product 19 cereal.

“I was in a commercial in the backyard eating cereal, which, that never happened,” he joked with Ripa, 54, and Consuelos, 53. Harmon confirmed he had just started high school at that point.

“So I'm picturing my own kids. Would that be embarrassing for you —” Ripa began before the Emmy nominee immediately interjected, confirming that it was “humiliating.”

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While people did not start to recognize him, the commercial "did change [his] direction a little bit," Harmon said. “I think I saw something, that crew, those people around, that I understood.”

Consuelos chimed in and said, “Also, the paycheck is nice. Did you get paid for that commercial?"

“My dad did. I think,” Harmon said, laughing. “I think they have laws against that now,” Consuelos added, and Harmon retorted, “Not then!”

Related: Mark Harmon and NCIS: Origins Star Austin Stowell Go Inside the Prequel Series: 'We're a Family Already' (Exclusive)

Since that first commercial, Harmon has gone on to star in several projects, from Freaky Friday to Moonlighting and St. Elsewhere, but he stuck with his NCIS character, special agent Leroy Jethro Gibbs, for nearly two decades.

Harmon starred in the military police procedural for 19 seasons until his departure in 2021. Since its premiere in 2003, the series has spawned five spinoffs: NCIS: Los Angeles, NCIS: Hawaiʻi, NCIS: New Orleans, NCIS: Sydney and NCIS: Origins.

ABC Mark Harmon on

ABC

Mark Harmon on "Live with Kelly and Mark"

Related: Mark Harmon Recalls Casting Austin Stowell as NCIS: Origins’ Young Leroy Gibbs: ‘That’s a Movie Star’ (Exclusive)

In a conversation with PEOPLE in 2019, Harmon revealed the secret to his success, which he credited to his late father’s advice.

“My dad taught me, if it’s not true, don’t worry about it,” the NCIS star said of his father, who died in 1990 at age 70. “I come from working stock, and I’m proud of that. You have to get up every day and just try hard”

At the time, Harmon explained that although his father had passed nearly three decades before, he continued implementing his father’s advice.

“Work your ass off, and don’t let the effort show,” he said. “Also: Treat people the same, not based on who they are or what they are. Show them common kindness. Don’t be colored by their fame or profession. I don’t get all excited by people blowing smoke up my ass. You have to stay honest.”

Harmon serves as a narrator and executive producer on NCIS: Origins, which airs on CBS Mondays at 10 p.m. ET.