I had one young lady (one of my regulars) who suddenly had the urge to go to the bathroom, but she had already started singing. The stage is at one end of the building and the powder rooms are at the other end.
Without missing a beat she headed to the bathroom with microphone in hand singing all the way there and all the way back!
Thank goodness we were using wireless mics. And I did use a Lysol wipe on it before putting it back on the stand.