This experience happened to me a number of years ago when I lived in California. I was at work and went into the bathroom. I had a headache that day and turned off the light in order to give my eyes a rest.
As my eyes became adjusted to the darkness (the only light source was a slight glow around the door frame), I became aware of a shadowy figure moving in the distance. It was too far away to actually be in the bathroom with me, but about 10 to 12 feet away.
I watched in amazement; these beings had distinct shapes with slim bodies and large bulbous heads. Even though they were shadowy, they appeared as solid as anyone in our normal three-dimensional universe would. I tried raising my hand and waving to the beings, one of them mimicked my gesture which showed that they were aware of me as well.
I should note that when the lights were on, the room appeared solid and normal, and even in the dark I could feel the wall when I touched it.
I had this experience several more times, often waving or signaling to the beings, but never making any greater contact. Then one day the portal was just gone. I left the job shortly after that and have never seen anything quite like it since.