i worked at little caesars for 3+ years and we used to **** with people all the time. i can only think of one time where someone put bodily fluid into a pizza though...
things we used to do to shitty customers include
loading sauce on there to where it's pretty much inedible(then say we can't replace it beacuse you specified you wanted 'lots of sauce')
put like 10 pepperonis on the pizza(supposed to be 32)
put black olive juice on pizza
put anchovie juice on pizza
only cut through the top of the pizza, and not the crust, so every piece you pulled ripped
hang up on people.
see how many times we could put the same person on hold. I held the record there for putting this lady on hold 13 times, and each time i picked up i used a different name 'hi this is chris sorry about the wait but can i put you back on hold?" and all she said when i finally took her order was "wow must be busy there" so then i told her it would be a 30 minute wait instead of the 15 it takes just so we could screw around some more.