During the first cinematic where it gives you the options to toggle the blood gore and swearing, wait until right before Eddie says the line that would lead to the option of turning on or off swearing. He sees one of the band members dancing on a very shaky ledge. While that band member is dancing on that ledge, he will be chanting a song that was done in Psychonauts by a couple kids in a few parts, but more notably by Raz himself in the level where you have to face four wrestlers to get a card. At the end of each match after you defeat them, Raz did the same dance and chant the song.
The headbanger that wears the goggles on all the Death Rack missions sounds identical to Raz, but slightly deeper.
To be rewarded with a music player that allows you to change songs while driving, find the Mouth of Metal upgrade near the beginning of your adventure. In The Deuce, look for red flowers around a mettalic structure. These are entrances to Motorforge. There is one located northeast of Bladehenge and another on the northeast side of the mountain where the Kill Master lives. Play the Relic Raiser Solo nearby and you can drive in with Duece. You will be rewarded with the music player.