I'm not sure when it started, I remember it a lot when I was a teenager but it may have even started when I was much younger. Typically it's the hide behind the door type of scare. My mammaw (she is in her eighties now) would hide behind a door or crouch down behind a chair for as long as she had to, probably didn't help her arthritis but she didn't care. Momma likes to wait outside of your bedroom door or bathroom door and as you open it she screams and bangs on it really loud, my brother likes this method as well. Madison likes to hide around corners or in closets, yes, the 6-year old partakes in the tradition. I have felt a mother's guilt for literally scaring the piss out of her on occasion. Just the one time, calm down. Joe will try and scare me on occasion, he typically uses the hide behind the door method. Other times he takes it to a whole new level and sneaks into the house and then when I hear stuff in the house I call him to see if he's the one making the noise and he tells me that no, he isn't home yet. This method is unacceptable. This method will eventually get 911 called on it.
My reaction to being scared is always a great topic of conversation. The stance I usally take is hands up by head, scream, put one knee into my stomach and crouch into a ball. FYI: This is ineffective in the event of a real attack. I will most certainly be killed if there is ever an actual "bad-guy" hiding in my bathroom.
My method of "scaring" is equally ineffective. I'll paint a picture for you with a recent situation. At momma's house, I see her walk out to the garage so I take my chance and hide behind a corner. While standing there with my hands up in attack position (why? I don't know) I of course start picturing her scared reaction and that makes me giggle a little inside. Well, that little inside giggle eventually erupts into pure hysteria and by the time she makes it back from the garage I am halfway to an unrecognizable heap on the floor. She walks by and the look on her face is pure confusion, and disappointment. I mean, here I am, heir to the throne and I can't even mutter out a "gotcha!"? Useless.
I also had the same situation with Morgan recently. I was already on the floor this time because I was going to grab his ankles as he walked by, bad move. By the time he walked by I was laughing hysterically and pawing at his legs. His reaction was similar to what it would be like to walk past a pile of dog shit, step to the side slowly and look down in disgust.