- "I started rapping way back in the day...."
- — Mark Grigsby
Mark Grigsby was a former Lead Animator and currently Animation Director at Infinity Ward. He lent his likeness and voice to SSgt. Griggs in Call of Duty 4: Modern Warfare, and sings the "Deep and Hard" during the credits. Mark Grigsby left Infinity Ward and joined Respawn Entertainment in 2010 to work on the Titanfall franchise.
In 2017, he rejoined Infinity Ward as Animation Director and worked on Call of Duty: Modern Warfare.
- "I started rapping way back in the day. I had a crew and everything. But my passion was animation, so I had to leave my crew and do my thing."
- "They were looking for inspirational songs for the end-credits. I definitely love Boot Camp Click and love Sean Price, so I'm like 'Let's get a Sean Price.'"
- "I still rap here and there."
- "We wanted something more personal and everybody wanted me to do it. So I did the end-song credit."