To "Olive Garden" a person means to enter into their bathroom in secret, open the tank of their toilet, and insert an entire loaf of bread and a can of tomato sauce. This will likely prevent flushing and create a priceless reaction when discovered.
"You just got Olive Gardened!"
"I just Olive Gardened her."
"Let's Olive Garden that person! It will be THE BEST."
"When I saw I had been the victim of a brash and relentless Olive Gardening I immediately vomited my dinner of delicious baby-back ribs into the very toilet that so offended me!"