It’s not really the same, but in metallic costumes and you want to make sure that, um, things are well protected from the sharpness of the metal. So I’ll wear under-armour jogging trousers. Apart from that, Loki keeps his underwear pretty simple!
Tom Hiddleston [x] (In period dramas, they say that the authenticity of the costume extends to the underwear. Does Loki have special pants?)