It’s hard to believe there was a time when anyone doubted that Elvis Presley was the King. After exploding onto the national music scene in 1956 with his hip-swiveling performance of “Hound Dog” on The Milton Berle Show, Elvis racked up hit after hit. But his famously controlling manager, Colonel Tom Parker, signed him up to make movies and soundtrack albums during much of the ’60s, when The Beatles and other newer stars were stealing his pop culture thunder. Elvis went seven years without performing live, until 1968, when he got back onstage for a TV special then simply called Elvis. It was a concert so successful and career-redefining that we now call it the ’68 Comeback Special. His stunning performance helped him regain his throne as the King of Rock ’n’ Roll. The new documentary Reinventing Elvis: The ’68 Comeback recounts how that consequential show wasn’t supposed to happen at all.