Glad When You're Bad is a song XANA wrote in Killer Music. Anyone who listens to it would enter a coma, and their heart would gradually slow to a stop. Odd was the first victim, as he was listening to the song on his CD player. Sissi was affected by the song in a similar fashion. After Yumi brang Sissi to the Infirmary, the Nurse turns on some music. Originally it starts out as classical, but XANA quickly changes the station to Glad When You're Bad " paralyzing the Nurse and almost Yumi. XANA soon broadcasted the song across the city. In an attempt to stall the Lyoko warriors, XANA played the song through the speakers and pipelines in the factory causing Jeremie and Ulrich to enter comas. The effects of the song did not reach Lyoko however. After the time reversion was activated, all victims of the song were reverted to normal. The song itself was still downloadable, but no longer caused the listeners to enter comas.
Not much of the song is known, but Odd can be heard singing "So glad when you're bad - bum bum bum bum bum..." in his dorm.