Surprising someone by wiggling your finger up one's anus (without them knowing), while yelling "SQUIGLY FISH!". Clothes may or may not be worn during this.
*John is standing in line at the concession stand waiting to get his popcorn*
April: SQUIGLY FISH!!!!
John: HOLY FUCK! YOU GOT ALL THE WAY IN THERE DAMMIT!
April: Yeah what can I say, I'm just good like that.