This is either a tour or the Mega Big Head.

Tours can be either for two or eleven chatters. Any member can take a group of other members on a Web tour with simultaneous chat-- next time you see one of those buses, drag your avatar onto the bus and see what happens! If you don't like the tour, you can always hit the "Back" button to return to your point of origin (or type in a URL in the Location box to go anywhere you want).
You can also set up a tour yourself (first define the properties of your tour) and then guide one (start the tour) in order to show your favorite spots on the web.

Mega Big Head is similar to a game, in fact it's a one person game (yahtzee) used solely to display an Avatar instead of the game picture in the chatroom. You start the program (download at the software site) and change back to the chat-room. That's it, your avatar is huge! (detailed tutorial)