Gemma (Katey Sagal) who starred in Sons of Anarchy appears in the pilot during the prison visitation scene, in a flashback scene.
Robert Patrick makes an appearance as his Sons of Anarchy character Les Packer. In real life he is a member of the Boozefighters MC.
Michael Irby and Robert Patrick were both in the The Unit (2006) which was produced by Shawn Ryan. Shawn Ryan and Kurt Sutter worked together on the The Shield (2002).
Perro is Spanish for dog.