Richie Sambora Tangos With John Stamos on 'Grandfathered' Set

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Richie Sambora guest starred on the latest episode of Grandfathered, and ET was there to see just how far his bond with star John Stamos goes.

"You're a rock god," Stamos told the former Bon Jovi guitarist.

"Thank you. I wouldn't go that far," Sambora responded.

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In Sambora's episode of the Fox sitcom, Stamos misses his granddaughter's birthday party, but calls in a favor from Sambora to throw the ultimate birthday bash to make up for it.

In real life the two have been pals for 20 years, and Sambora told us they always have fun together.

"I love music and he's our first big musical star so I'm so grateful for doing this," Stamos said.

Even after all their years of knowing each other, Sambora is just as baffled as everyone else when it comes to Stamos' appearance.

WATCH: John Stamos Is Out of Rehab and Looking Incredible

"He just looks the same. He hasn't changed since I've known him," Sambora said. "I'm like, 'Did you find the Fountain of Youth or something, man?'"

airs Tuesdays at 8 p.m. ET/PT on Fox.