Can you do multiple/double exposure on a Nikon D3100 camera?

I want to know how to take a picture so that you can appear twice in one photo. I have a Nikon D3100 and I'm just wondering if you're able to have that option on the camera.

I'm not sure if you can do it in your D3100 or not. I can in my D90.

Go to the "Shooting Menu", and see if there's an entry for "Multiple Exposure". That is where it is on my D90, and since Nikon tends to use a common interface, if you have that function, it would likely be there.

http://www.althephoto.com

I know I can overlay two photos only when I shoot in RAW on my Nikon D40. I assume that function is also on your camera

Yes, it is possible, but you're much better served with image editing software. The image combining feature in any camera is pretty rudimentary, just a simple overlay. You can't cut and paste parts of different images together.

With Photoshop, or free alternatives like GIMP or Paint.NET, you have much more leeway over how to work with the images.