Could it possibly be your mannerisms? If you were adopted young, you may smile very similar or express/speak so alike and that's what they meant. My husband and I look nothing alike, but we've heard on more than one occasion that we look like siblings/family. Yeah it sounds super weird to think about, but I understand what they mean as I've seen that in other couples as well. (I know you're mother and daughter, not a couple obviously!! Just stating how two completely different people can seem so alike!)

No. It's a reference to the famous line from the movie "Full Metal Jacket."