I just tried if the Winamp 2 easter egg still works in Winamp 5.5. You may remember this:

The easter egg does work in Winamp 5.5, but it doesn't have anything to do with the Winamp slogan. By activating it, you can unlock a transparency effect that changes based on the music you play. It sounds really vague, but you have to give it a try. Here's how to activate the easter egg:
1) Give Winamp's main window focus.
2) Press the following keys:
N,
U,
L,
Escape,
L,
Escape,
S,
O,
F,
T.
Make sure that you've chosen the Bento skin before trying it.