Commentary tracks on DVDs have been around for a long time. Now they’re on video games. Half-Life 2: Episode One has a mode where you can play the game with interactive commentary. From Waxy.org:

As great as the game was, I was blown away by the in-game Developer Commentary system. Each bit of audio is a “commentary node,” a little floating speech icon that can be activated by aiming at it and hitting the “use” button. The dialogue then plays, with additional information about who’s speaking and the length of the clip. (See videos below.)

Most of the game’s 115 nodes are audio only, pointing out interesting tidbits about the scene you’re currently in, such as the visual design, character dialogue, or gameplay. Some of the best examples discuss the iterations a stage or puzzle went through, why original versions didn’t live up to expectations, and how they reached their final design. It’s a fascinating glimpse into the minds of the developers, very much like sitting next to them as you play through at your own pace.

But a few commentary nodes do much more, taking over the player’s view to show them something hidden or entirely new. I’ve captured video from some of my favorites.

There are several videos there. I only watched the first one since I haven’t played the game yet and didn’t want any spoilers. Luckily, that first one didn’t reveal too much of the plot.

Here’s a video of two olde tyme swing dancers set to modern hip hop music. I might try a few of these moves out at the next wedding or bar mitzvah.

(video requires Flash 8)

Here’s a site that has scans of a German children’s book on reproduction. Might not be safe for work. Of note, there is a goatse-like birth.