Some of the situation you guys have mentioned, I haven't encounter personally yet but I have thought about (in case someone ask).
1. Outline of Binder or feeling binder
Excuse: "It's an undershirt, I sweat a lot", "I play a lot of sports and over the years it has damaged my back. It's a back brace."
2. Looking young/Being Short/etc.
Excuse: "Haha, all Asians look young...seriously, there's a benefit and there's a downside to it."
"I need to work out to get rid of my baby fat, is all"
3. Voice
Excuse: "It's from singing all of my life.", "Haha puberty was not kind to me."
4. Are you a guy or a girl?
Excuse: "Guy of course, can't you tell?"