Short for shenanigans. However, unlike shenan (also short for shenanigans), this is used to call out tomfoolery on things that are little and cute. Like bunny rabbits, rainbows and babies for example.
The combination of the words Shenanigans and Antics.
When something is so crazy, so F-ed up, or so stupid that it is used with the word "Shenantics", the two combined words instead.
Besides, no one really used the word "Shenanigans" seriously unless your'e over 40.
1.
Mark: "F*ck Nick, I am SICK of your SHENANTICS!!!"
2.
Lacey: "I justwant to get wasted tonight.."
Jenny: "TIME FOR...."
Lacey: "SHENANTICS!"
3.
You: "The a-hole buss driver saw me here but didn't stop.." :(
Me: "F*ckin' shenantics man!"
Brian: "Dude, remember that time Kevin passed out and we pranked him by sticking his hand in a bowl of gravy, and when he woke up he smeared it all over his face?"
Zack: "Fuck yes, man, I'm just glad nobody recorded the mass shenannigasm we all had when that happened!"