Shift + D not doing what I want

Hello

I’m trying to duplicate a plane with Shift + D, and then change the material to Halo without the original plane doing the same thing, but it will not let me. I’ve done this before and it worked, what is it that has changed/what have I done wrong?

Why I want to do this:

The reason I want to do this is that the first Plane is set to Wire, and if I make a duplicate and set that to Halo it gives it a cool digital look, as shown on the image below.


When you duplicate it, it will have the same material as the original object. In the material panel press the number next to the material name to make it a single user, then adjust the new material settings.

Thanks!

Don’t know how I got passed that the first time…