Despite not enjoying shaving his hairline, he reveals that it helped him get into character.
"But it was great really. I found something quite exciting about transforming the way you look a bit, especially as an actor, because it makes you feel different. So whilst I didn't relish having my forehead bicked every day, because I was worried it wouldn't grow back, it works really well in the movie."
During this part of filming, the British star jokes he "was under a hat all year."
He adds, "Which is sort of fine a lot of the time, but it's a bit of a pain when you're going to dinner or something, but it's alright. What can you say? It's all for the art," he quips.
In addition to his transformation, he reveals Sir Elton let him read through his diary. "That was such an exciting thing... absolutely hilarious as well," Taron says. "They are so funny."
He shares an example of what the dairy entries are like, and explains "they're very economically written."
"It will be something from 1972 or whatever, 'The washing machine is broken again. Wrote a song called "Honky Cat." And that's all it says for a day." Egerton continues, and says with a cheeky smile, "Another one of my favorite ones is: 'Went out for dinner last night, did a moody, smashed a plate of french fries.'"
Furthermore, Taron's co-star Richard Madden also dishes on Rocketman (he plays John Reid) and the one thing that made him feel "naked."
"There's nothing more terrifying... I felt naked when [I] sing and dance. You're kind of showing different things and I was really terrified of it," the 32-year-old Scottish actor reveals to E! News. "I worked really hard to try and make sure that I wasn't thinking about my singing voice on the day [of filming]. I was thinking about the storytelling, instead."
To see the full interviews with both Madden and Egerton, watch the video clips above!