The first Elvis impersonator was Brendan Boyer, a member of the Irish Show Band that
   performed in Las Vegas in the early 1970s. "Elvis used to go to the Stardust to watch him. Elvis enjoyed the  impersonation, especially the trilogy."
One time he was singing Hound Dog when he saw a guy in a white hat & coat
 shaking his cane at him angrily , suddenly he realised it was Elvis having a joke ,
and alsmost as quickly as  he'd appeared he was gone !
What a story! I love it.
Stardust Hotel: Elvis Sez
    "Brendan Boyer used to do an impression of me that was so cool,
I just had to catch him at the Stardust after all my shows.
I would get a mess of beers for the  boys and let him do all thework, y'know what I'm saying?"

It should also be pointed out that one of the reasons Elvis loved to play Las Vegas was because on his night off he could slip down the road for a jar and catch Brendan Bowyer and the Irish Showband recreating the atmosphere of a typical rain-soaked night in a miserable marquee somewhere outside Glenamaddy. Who knows what plans were hatched when El and the lads got together backstage,
To this day Mr. Bowyer remains tight-lipped. So it's still unclear whether Elvis actually recorded that other Irish anthem 'The Hucklebuck'.