Dream characters are just creations of your mind. If you couldn't imagine anyone acting different than you, then everyone would act the sam ein a dream.

But, I'm pretty sure you can imagine how different people would act, or how your friends or parents would act.

Everything with dreaming is individual because it is contained entirely within your own mind.

You could create copies of yourself in your dreams if you wanted to. You know what, that actually sounds rather cool. 200 other Me's to look at would be fun.