My department has always done a lot of different things. Many years ago we were called 'Computing Services' ('University of Toronto Computing Services' if you were being formal), and one of those things was a bunch of modems on a Sun 4. Of course, we had a greeting banner:

U of T Computing Services.

login:

(roughly what you saw if you dialed in.)

One April 1st, a co-worker changed this to 'U of T Confusing Services'.

The best part of this (as far as I'm concerned, because I like subtle April Fools' jokes) is that hardly anyone noticed; after all, who really reads a login banner that you see routinely?

The Sun 4 is long gone, and so are most of our modems. But one modem remains, and to this day (even after several changes of hardware and operating system, and two departmental renamings) it still greets callers with:

U of T Confusing Services.

login: