In the Closet

A lot of weird things have happened over the years that involved doorways, particularly closet doors. As a very young child, for instance, I inspected the closet every night before bed; sometimes, in the middle night, I had to re-inspect them only to discover that they were... different.
There was a time that I had to share a room with my brother. He was four years older than me and resented having to share a room with a kid brother but that's the way it was. One night, he had some friends sleep over. I tried to be cool about the whole thing but I secretly liked having older brother-types around. It made me feel safe.
We read comic books before bed, reading some of the panels out loud. We eventually turned to reading the ads out loud, too. Would x-ray spex really work? Wouldn't it be cool if they did? What would you do with them?
One ad was for a life size, glow-in-the-dark poster of Frankenstein's monster. Wouldn't that be awesome? What if it came to life? Would that really scare anyone? How would you display it? Even as we laughed about it, I looked at the ad in my own comic book and shuddered a bit. It seemed creepy, late at night. Even the comfort of a room full of, well, boys didn't abate the terror of the monster coming to life and killing us in our sleep.
Eventually, the lights were turned off and we drifted off to sleep. I woke up with a chill. I could hear the other guys sleeping but the hair on my arms was standing up. Something was wrong. I could make out the sound of the closet door opening. I slowly rolled over and looked through a slat in the bunk bed. The closet, about 6 feet away, had a pocket door and made a rolling sound as it opened. As I watched, the door just finished opening all the way. Slowly, Frankenstein's monster faded into focus. He looked just like the ad so I assumed that my brother and his friends were playing a prank on me... except that I could hear them sleeping. I sneaked another peek and the monster's head had turned! That wasn't part of the ad nor could a paper poster do that! I figured I had to be dreaming but my heart was racing, my throat was dry, I felt like I was dying.
As I worked up the nerve to scream for help (risking forever being branded a loser or worse by my brother's friends), I heard the door closing. I peeked one last time as the door shut all the way. Suddenly, it was warm again. I could move freely and quickly ran to the bathroom, just to catch my breath and be away from the scary... thing.
In the morning, I braved a look at the closet door when no one was around. There wasn't any sign of string or anything that could have remotely opened the door. Much less was there any rolled up poster or anything that a poster could have been attached to. What I saw wasn't something that teenaged boys could have faked. And, knowing teenaged boys, they would have teased me either in the moment or in the morning.
I'm still not sure what it was.