What is happening to the German version of Wikipedia? I just checked de.wikipedia.org and ended on google.de. Now I rechecked and got the main page of Wikipedia but with the favicon of Google! Weird?

Can't reproduce this here... does this still happen if you empty your cache and try again?

No, you're right. Its all back to normal for now. Unfortunately I didn't take a scrennshot.

are you sure it wasn't a miss-click? But if was, then you wouldn't see the favicon changed.
And about the changed favicon, it was probably because it was stored on cache rather than reloaded from wikipedia.
Does your ISP uses proxies to serve pages?