Willie says

Brett's latest favourite song is a Willie Nelson tune:

Shotgun Willie sits around in his underwear
Bitin' a bullet, pullin' out all of his hair
Shotgun Willie has got all of his family there

When Willie says "underwear" Brett laughs and laughs.

Randy has a customized version:

Shotgun Brett sits around in his underwear
Suckin' his thumb, pullin' out all of his hair
Shotgun Brett has got all of his family there

Brett says, "I do have all my family here: mommy, daddy, and me!"