World War 2 Comedy Film?

I'm trying to find this old black and white movie about WW2. I've never seen the whole thing but I remember a scene where one of the american soldiers is dressed like a German scientist and challenges the colonel to yank his beard to prove it's fake. The colonel backs off, but then one of his superiors walks in saying that the REAL scientist is still in Germany and chastises the Colonel. Afterwards the Colonel screams out for his aide Schultz. It's a little vague and there might be a few errors, but this is as much as I remember. If someone can help it would be greatly appreciated.