After the show, Elvis introduced himself to Johnny and his then wife Vivian and invited them to his next show at the Eagle's Nest. Which Johnny remembers as a flop since it was an adult establishment and his biggest fan base was teenage girls.
On December 4th, 1956 at Sun Studios in Memphis, Carl Perkins was recording for Sam Phillips. Johnny Cash sat in to listen. Then in walked Elvis Presley and Jerry Lee Lewis followed. This event culminated in a jam session that would be dubbed "The Million Dollar Quartet". It create a fever among collectors and even inspire a Broadway musical.
A few years later, after Elvis went off to Germany in his stint in the United States Army, Johnny Cash brought a little bit of the 'spirit' of the king on nationwide TV. The show was called "The Vel's Ford Town Hall Party". Johnny cracked a few jokes regarding Elvis (Elvis who?) and then flipped his hair into a "Doo wop" pompadour and began swiveling his hips singing "Hearbreak Hotel" in a performance that Time magazine listed in the Top 10 Elvis Impersonators.
Sadly, the King probably never saw it.