I once appeared in "Pippin", a musical loosely based on the life of Pippin, the son of Charlemagne.
I changed with the actor who played Pippin. He was good-looking, although a little on the short side (5'8-9" ?), and had a great voice.* Like me, he was fairly hairy.
We wore leotards with "speedos" underneath. They were the same color so as to keep from showing through. Our costumes hung just barely below our groins and butts, so we occasionally "flashed" during certain movements or in some positions.
He usually arrived wearing his speedos in lieu of underwear. I was more "who-gives-a-fuck!" and would change in and out of my regular Jockeys. However, a few times he did arrive wearing underwear and would turn his back while changing into his speedos. Once or twice, though, he turned towards me, I guess to avoid having to expose himself to the rest of the cast. Although I could tell by the "bump" in his speedos he wasn't packing that much, nevertheless I was still surprised that his dick was so small, about the same size as mine -- really small and almost buried in his pubes. Caught me off guard a bit. I don't know why it should have because I too am a totally masculine-looking guy with a really small cock. Unlike myself, though, he was obviously really "shy" about it.
Oh, yeah, BTW, you occasionally saw others when they were changing.
* For those who are curious, as far as I could tell he was straight, although I never saw evidence of a girlfriend.