When I aim this trigger, it all goes red.
Do you have a bounty 'cause you got a "M" on your head?
Listen up, buttercup. This joke is for dummies who don't know about hairlines. The joke is saying the person has a receding hairline that makes the shape of an "M" on their forehead. The person making the joke is pretending to aim a gun, and the red is the laser pointer to make fun of the hairline, which is rude. BOOM! Roasted!