Watch: Eric Clapton brings out John Mayer at Budokan

The thing that can make an already amazing concert more phenomenal is a stellar special guest. Classic-rock guitar god Eric Clapton delivered when he invited John Mayer to join him onstage in Tokyo over the weekend.

Clapton started his five-night run in the city's iconic Budokan with a bang on Saturday, bringing Mayer out for a nearly eight-minute-long cover of J.J. Cale's "Cocaine." Clapton also dusted off sold old classics during his 15-song set, playing songs like "Pretending" and "Wanna Make Love to You" live for the first time in years--plus, he returned to playing an electric version of hit "Layla" for the first time since 2013, when he played it during his 50th anniversary tour.

Mayer has both been a special guest and featured some of his own onstage as of late--he's joined Clapton onstage in the past, and at his own performance at Budokan last week, he was joined by fellow singer-songwriter and guitarist Ed Sheeran. The two played Mayer's "Belief" and Sheeran's own hit ballad "Thinking Out Loud."

It's no surprise that Mayer is also part of the lineup for Clapton's Crossroads Festival in Dallas this fall and has the distinction of being one of a small group of artists who have been invited to perform at every festival. This year's lineup also includes Bonnie RaittCitizen CopeGary Clark Jr.Jeff BeckJoe WalshLos LobosPeter Frampton, Sheryl Crow, Tedeschi Trucks BandVince Gill and, of course, Clapton himself, who will play both nights of the festival.