Jerry Seinfeld has coined his temporary takeover on “Live!” for Regis Philbin as “Operation Smooth Transition” but relations between the two TV titans were not always so peaceful.

Once upon a time, Seinfeld, who will sit beside Kelly Ripa as the first Philbin fill-in until Wednesday, strong-armed Philbin into an unfunny “Seinfeld” cameo that still has the TV talker steaming mad.

Philbin, 80, writes of the “minor (but everlasting!) quibble” in a chapter dedicated to Seinfeld in his new memoir, “How I Got This Way.”

In 1994, Philbin and then-co-host, Kathie Lee Gifford, were tapped to guest on the “show about nothing” in a now-famous episode dubbed “The Opposite.”

The script called for Kramer (played by actor Michael Richards) to promote his new coffee table book on “Live!” where he would spew hot coffee all over Gifford.

The real outrage, Philbin writes with characteristic zeal, was that “the Seinfeld writers had, for some reason, decided to have me react to Kramer’s antics by repeatedly declaring, ‘This guy’s bonkos!'”

“I had never said the word bonkos in my life. I’d never even heard of the word!” Philbin writes. “I mean, it just wasn’t funny — and why should I become the only Seinfeld guest in history who never got a laugh?”

Philbin appealed to the writing team and Seinfeld himself — yadda yadda yadda — but no one would budge.

“Jerry, too, thought bonkos was hilarious,” Philbin pouts.

Just as Philbin predicts, his ‘bonkos’ lines bombed with the audience.

“Kramer was a hilarious smash. Me and ‘bonkos’ — on the other hand — we got nothing, not even one laugh. Only silence. I mean, deafening silence,” Philbin complains.

“I will never forget that silence, nor will I ever get over it,” Philbin adds. “It remains embarrassing to this day.”

Philbin’s grudge appeared under wraps Monday when he praised Seinfeld and Ripa’s first show together, telling Miami’s WPLG that it was “a lot of fun.”

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