In case you were wondering just what that ITG/DDR looks like, they stand for "In the Groove" and "Dance Dance Revolution". They are arcade games and are basically Simon Says for the feet to dance music, and are usually one player on 4 pads that are oriented as up, left, down and right arrows. Sometimes, people play two pads at once.
This is what it usually looks like:
http://www.youtube.com/watch?v=oh5Qq6aLcs0&feature=related Then, you can make up choreographed routines:
http://www.youtube.com/watch?v=_VRad-Ql228&feature=related Notice that you hit arrows in the order they come up on the screen, hence the Simon Says part.
And... this is what it degenerates to (at this point, the guy is using the back bar on the machine as an upper body support so that his legs are all that moves, but regardless, it is extremely hard):
http://www.youtube.com/watch?v=9BGOqynUaGU&feature=related I can't play nearly as well as the last video, but I don't use the bar as an aid either. My best abilities are only doing 1100-step songs that are about 3 minutes in length.
You should try it! It's fun. Jesse, Cesar and Eric Tran are all great at it.