Quake 2 Easter Egg - Rubber Duckie

1. This takes place in the Lost Station (train.bsp). It's a secret level, which you get to by diving underwater at the beginning of the Comm Center (base3.bsp).
2. Near the beginning of the level you'll find a train which shuttles you between two stations. Take the train to station no. 2.
3. From there, board the train and ride it around 13 times.
4. There is a grey panel across the wall. Look how it's changed!