The Aryan Brotherhood member sported a common neo-Nazi tattoo reading "88" on the back of his head. This is in reference to "H" being the eighth letter of the alphabet, symbolizing the letters "HH". This is short for "Heil Hitler".
Grey tells Nolan "once more with feeling" referring to him redoing paperwork. "Once More with Feeling" is the name of the of the musical episode of Buffy the Vampire Slayer created by Joss Whedon. Nathan Fillion, who plays Nolan, was in Buffy and several other Joss Whedon works.