LOS ANGELES, CALIFORNIA: In a sensational revelation, John Stamos has opened up about a jaw-dropping incident from his past when he stumbled upon his then-girlfriend, Teri Copley, in bed with none other than Tony Danza, as per Entertainment Weekly.

The shocking revelation is detailed in Stamos' upcoming memoir, 'If You Would Have Told Me,' set to hit bookshelves on October 24.

John Stamos and Teri Copley's whirlwind romance

Stamos reminisces about the beginnings of his relationship with model and actress Teri Copley, recalling their casual first date in the 1980s, which ignited an instant spark. He was smitten, envisioning a future as a stepfather to her daughter, Ashley, from a previous relationship.

Stamos gushes about his affection, stating, "I could spend the rest of my life with her. Who knows if I'll ever find love again? Why not take a chance?"

John Stamos got troubled by a subtle shift in his relationship with Teri Copley

More than a year into their romance, a subtle shift in their relationship began to trouble Stamos while he was away for work commitments.

"I call her from the road, but the girl who breathlessly picked up the phone after one ring is now giving me busy signals and dial tones," Stamos writes. The silence was unnerving, and he sensed something amiss.

As his concerns grew, Stamos learned that Copley's ex-husband, Chip Mayer, was in town for the weekend. Worried, he rushed to her Valley residence, only to find it in darkness. A car in her driveway piqued his curiosity, a vintage 1957 Porsche 356 Speedster. His gut told him to investigate further, and his discovery would haunt him.

John Stamos finding out about Teri Copley's affair with Tony Danza

Stamos recounts the moment he found his world unraveling: "There's a hairbrush, keys, boxing gloves, and a half-unrolled poster of my girlfriend, naked, barely covered by a white sheet. Half of her butt is showing. I've never seen this poster before."

The house was locked, but he remembered the guesthouse where they occasionally slept. Stamos describes the heart-wrenching sight: "My Tiny Dancer is in bed with Mr Porsche Speedster. They are sleeping. I can't tell who he is, but I recognize Teri's ass barely covered by the sheets. It looks like her new poster."

Overwhelmed by the betrayal, Stamos reflects on the moment, admitting, "I try to hold back tears. Time slows until I'm frozen. I can't breathe. A few tears roll down my face, and it pisses me off. They snap me out of my daze, and I feel angry and confused."

Uncertain about how to confront the situation, Stamos opted to leave rather than engage in a confrontation. He left with the poster inscribed with the words, "My Dear Tony, I'll love you forever. XO, Teri."

The revelation left him wondering, "Tony? Who the hell is Tony?"

It wasn't until he was driving back home, with Elton John's music filling the car, that Stamos had an epiphany about the identity of his romantic rival. As he listened to the lyrics, "Hold me closer, Tony Danza," Stamos penned his realization.

John Stamos acknowledges Tony Danza's impact on his career

In a later chapter of his memoir, Stamos acknowledged the unexpected role that Danza played in his own career. Stamos attributes Danza's beloved 1980s show, 'Who's the Boss?' with boosting the success of his own sitcom, 'Full House,' which premiered a few years after 'Who's the Boss' and garnered a substantial following during its first season.

Reflecting on this, Stamos writes, "If you would have told me the day I walked into that room and caught my true love in bed with another guy that his show 'Who's the Boss?' would launch 'Full House' into a bona fide hit, making me a household name... Well, what can I say? Thanks, Tony Danza."

Both Danza and Stamos portrayed similar roles on their respective shows. Danza starred as Tony Micelli, a former professional baseball player who becomes a housekeeper, raising his daughter, across eight seasons of 'Who's the Boss?'

Stamos, meanwhile, took on the role of Jesse Katsopolis, an exterminator by day and a rock star by night, in 'Full House' and its recent sequel series, 'Fuller House.'

Stamos' tell-all memoir, 'If You Would Have Told Me,' is set to be released on October 24, promising further insights into the actor's tumultuous past and rise to stardom.