Jerry Schilling (long-time friend, bodyguard and assistant to Elvis Presley) answered this question in his interview in the September 2007 issue of Record Collector magazine. Jerry said:
The actor Jack Lord [star of Hawaii 5-0] comes to mind. We'd finish the first show in Vegas and Elvis would say, "Would you take Mr & Mrs Lord up to the suite? I'm gonna have dinner with them."?
He always spoke softly, because they were real classy people. He really had a reverence around Jack Lord. It was amazing.?
The only other people that I saw Elvis have that kind of respect for were Priscilla's mother and father. They're wonderful people.?
Source: ? Record Collector magazine?