this part in that Shack interview is interesting:
"He still regrets the band allowing one character in Hot Tub Time Machine to wear an
Iron Maiden shirt throughout. “That was a litmus test of what happens if you grant the licence and take the fee. We’re not bloody Spinal Tap or Steel Panther.” "
I remember Hot Tub Time Machine as a a cool comedy, the character who wear Maiden shirt was a little goofy but it was nice to see a reference to Maiden in that movie.
And do they need promise when a character wear sth... Then there are a lot of movies where people wearing Maiden tshirts. For example this small budget indie / festival movie has its main actor wearing Maiden Senjutsu tshirt on a lot of scenes, even in the Letterboxd poster: