From the IMDb:
To celebrate Angie's 30th birthday, Will throws a big party re-creating Ozzfest; Douglas takes Graham shopping to help him find the perfect gift for Angie.
At the end of this episode, with her 30th birthday falling apart, Angie at least got to get up on stage and sing this Slayer number.
"Raining Blood" is a song by the American thrash metal band Slayer. Written by Jeff Hanneman and Kerry King for the 1986 studio albumReign in Blood, the song's religious concept is about overthrowing Heaven.
The song is four minutes and fourteen seconds in duration. It ends with a minute of rain sound effects. Described as a "classic" by Allmusic, it is noted by fans as one of Slayer's most popular songs. As an almost permanent addition to their live sets, both Hanneman and King acknowledged it as their favorite song to play live. Many of Slayer's live performances of the song have been captured on the band's live albums and also multi-band compilation albums including MTV2 Headbangers Ball.
There have been many appearances of the song in the media and elsewhere, including the South Park episode "Die Hippie, Die", and the video games Grand Theft Auto: Vice City and Guitar Hero III: Legends of Rock, where it is considered difficult to play.
A lifeless object, alive
Death will be their acquiescence
The sky is turning red
Return to power draws near
Fall into me, the sky's crimson tears
Abolish the rules made of stone
Pierced from below, souls of my treacherous past
Betrayed by many, now ornaments dripping above
Awaiting the hour of reprisal
Your time slips away
From a lacerated sky
Bleeding its horror
Creating my structure now I shall reign in blood
Raining Blood lyrics © Universal Music Publishing Group