Born in Lagos,[3] Badejo was of Yoruba descent[4] and was the son of the director general of the Nigerian Broadcasting Corporation.

[2] He studied in Ethiopia, then in the United States before finally moving to London to specialize in graphic design.

[2] Badejo was discovered in a Soho pub by a member of director Ridley Scott's casting team,[5] who had been searching for a candidate to play the titular creature in his science fiction horror film Alien.

[6][7] He was described as "mild-mannered" and "withdrawn" on set, and special effects supervisor Nick Allder said "To have been the center of attraction… it was a bit of a shock to him.

"[8][9] Alien was released in 1979 to significant critical and commercial success,[10][11][12] and Screen Rant wrote in a retrospective review that he "effectively brought the Xenomorph to life ... Badejo certainly helped make the creature one of the most recognizable monsters in horror.