Short answers, pulled from the story.
Cloud Strife was designed by Tetsuya Nomura for the 1997 game Final Fantasy VII, with his backstory and personality developed by director Yoshinori Kitase and writer Kazushige Nojima. The team wanted a mysterious protagonist who acted atypically for a hero, in contrast to the multi-character structure of Final Fantasy VI.
Cloud's false persona resulted from four years of experimentation by Shinra scientist Professor Hojo following exposure to Mako radiation and injections of Jenova's cells. His mind constructed a new identity based on his friend Zack Fair, a SOLDIER who died at the outskirts of Midgar, which inadvertently erased Zack from Cloud's own memory.
Takahiro Sakurai has voiced Cloud in Japanese since Kingdom Hearts, recommended to director Nomura by voice director Teruaki Sugawara. In English, Steve Burton voiced Cloud in most adaptations until being replaced by Cody Christian for Final Fantasy VII Remake; Christian won Best Lead Performer at the 2024 Golden Joystick Awards for Final Fantasy VII Rebirth.
According to Super Smash Bros. director Masahiro Sakurai, Cloud received more fan requests for inclusion than any other Final Fantasy character, and Sakurai felt no other candidate matched his popularity. Cloud was added as downloadable content in December 2015 alongside a Midgar stage.
Sharon Packer identified Cloud as exhibiting dissociative identity disorder, while Katie Whitlock read his fragmented memories as consistent with post-traumatic stress disorder. Critics have also cited him as one of video gaming's first unreliable narrators, with comparisons drawn to films such as Fight Club and Memento.
Nomura designed Squall Leonhart for Final Fantasy VIII with a similar anti-hero persona following Cloud's success, and was explicitly tasked with creating a female version of Cloud for Final Fantasy XIII, resulting in Lightning. The Final Fantasy X team deliberately built a more cheerful protagonist in Tidus as a direct contrast to Cloud's emotional reserve.