Deadpool Annual #1 2014 NM-

Deadpool Annual #1 (2014) reveals the origin of the white caption boxes that represented an internal monologue in previous Deadpool comic series, explaining that they were the consciousness of the villain Madcap trapped inside Deadpool's mind. The issue is written by Ben Acker and Ben Blacker. 

The issue is split into two main parts, bookending the Daniel Way Deadpool series where the white caption boxes appeared: 

• Before Secret Invasion: Deadpool is on a rooftop in Hell's Kitchen, attempting to assassinate Matt Murdock (Daredevil). His attempts are continuously thwarted by various heroes like Spider-Man, the Avengers, and the X-Men coincidentally fighting villains in his line of fire. He is interrupted by the unharmable Madcap. Daredevil and Thor arrive and, to stop both villains, Thor strikes them with lightning, reducing them to ash. When Deadpool regenerates, Madcap's consciousness becomes an unwanted guest in his head for the next several years, manifesting as the white caption boxes.
• Just before Marvel Now: Deadpool is on the same rooftop, attempting the same assassination. This time, he uses a bomb to distract the heroes. Luke Cage finds the bomb and punches Deadpool unconscious, at which point Madcap takes over Deadpool's body. When Deadpool awakens, he and Madcap agree to separate. They have Thor and Luke Cage pull Deadpool apart, and when he heals, both Deadpool and Madcap are separate entities again. Madcap leaves, and a newly-solo Deadpool is then beaten up by Daredevil, suddenly missing his chatty companion.