Shit Switch
Referring to the point where when your standing up pissing, and you feel the urge to shit, so you quickly pull your pants all the way down and spin 180 degrees to sit on the toilet.
Bro, Its a good thing I Shit switched before I shit my pants.
Shit 'N Switch
The act of defecating yourself and then going back to change into different underwear, shorts/pants, etc. before anyone noticed you were gone.
Jimmy sat in the lecture trying to hold in his massive log until his bowels gave in. In a span of 5 minutes, he left and came back in a pair different colored shorts that went unnoticed by everyone, and resumed normalcy. Jimmy successfully carried out a Shit 'N Switch.