Harrison's "Elvis" casting was announced back in December 2020. The first thing the actor did after he was picked to play B.B. King, aka the King of the Blues, was start researching the musician's history. "I was like, 'OK, I should probably start looking up interviews of him because I have three weeks [before filming]. I heard Austin Butler's been prepping for two years,'" he said. "That was my first task. I'm like, 'OK, let's start.' I got a playlist going, started listening to the music, and getting myself hyped up."
As one of Butler's scene partners, Harrison noted that the actor was so humble. "Sometimes when you meet certain actors, you kind of get nervous because they get really serious and 'actory.' But I think Austin and I were kind of like, we're very serious about our craft, but we're also like, 'Let's have a good time as B.B. and Elvis would,'" he said. "I think my job as B.B. King in that space and as Kelvin to Austin was to bring some light and some levity to the situation, while also just encouraging and empowering him through the final run of the race as he played Elvis."
