I just had my first session where I caused someone to break cover by just being too weird.
There's this inflatable cube that can launch you up to higher levels, but you can inflate it and deflate it as you please at distance without breaking your disguise. So I threw it into a doorway and was just idly inflating and deflating it while milling about elsewhere.
Some poor guy was so confused about what this thing was doing that he ended up acting just funny enough that I was able to pick him out and blast him senseless.