Shannanigans are similar to shenanigans, but in the case of shannanigans, they are perpetrated by Shan. It can be assumed that everything Shan does is shannanigans.
When you beleive that there is deception or foul play afoot, and you want to be the one that calls it.
You stand up, point at the object/person that you believe to have been involved in the deception and yell "Shannanigans!!" as loud as you can as to attract attention.
However there is an element of risk involved. If you are wrong about the "Shannanigans" call and there is nothing sinister about the situation, you will look like a douchebag
everybody had a hearty chuckle at Jerry when he called Shannanigans on Tom, thinking that he has slept with his wife. Only to find out that he was dead wrong.
acts of individuals and/or groups of people, whos purpose is simply to have fun, most of the time at others expense, but with out hurting any one.
our shennanagins are cheeky and fun, Farva's shennanagins are crule and tragic. Which really makes them the opposite or shennanagins. (Evill shennanagins!)