Short answers, pulled from the story.
Mega Man was created by Akira Kitamura for Capcom, with the first game released in 1987. Artist Keiji Inafune produced refined character artwork based on Kitamura's original pixel art design.
Capcom USA Consumer Products Division President Joe Morici changed the name from Rockman to Mega Man because he felt the original title was "horrible". The name Rockman referenced rock and roll music, pairing the character with his sister robot Roll.
Illustrator Marc Ericksen painted the Mega Man 2 North American box art in roughly a day and a half with no prior knowledge of the character. He depicted Mega Man holding a pistol after his art director instructed him to, not knowing the character's signature weapon was an arm cannon.
Mega Man can copy the special weapons of boss robots he defeats, using his Mega Buster arm cannon as his standard attack. Across the series he gained additional moves including the slide in Mega Man 3 and the charged shot via the New Mega Buster in Mega Man 4.
Mega Man first appeared in animation through Captain N: The Game Master, voiced by Doug Parker. He also starred in a dedicated animated Mega Man TV series voiced by Ian James Corlett, and in a 1993 three-episode Japanese anime OVA titled Mega Man: Upon a Star.
A February 2010 Famitsu poll ranked Mega Man twenty-second among popular video game characters. The 2011 Guinness World Records Gamer's Edition placed him twenty-third, and GamesRadar ranked him twelfth among the most memorable and influential game protagonists in 2012.