From the Doc over at FECC - Fooling around between shows with "Whipper" Billy Watson, backstage at the Maple Leaf Gardens, Toronto ON- Tuesday, April 2, 1957
Elvis' first set included two unreleased covers, Charlie Gracie's "Butterfly" and Smiley Lewis' "One Night."
Presley had waxed the Lewis number in February, it would be issued by RCA in October 1958.
Billy Watson was a famous Canadian professional wrestler and part of Elvis' security team in Toronto.

John Sebert/ Library and Archives Canada, accession 1998-045 NPC

With "Whipper" Billy Watson and wrestling promoter Frank Tunney, backstage at Maple Leaf Gardens, Toronto ON - Tuesday, April 2, 1957 - with thanks to the Doc at FECC for the photos and details

Backstage in Toronto, ON on April 2, 1957

Thanks to fredrocker for 2 of the the photos - more photos here:
Elvis In Toronto
Elvis In Toronto