Yellowhead

From LittleBigPlanet Wiki

Yellowhead was the name of the prototype presented to Alex Evens and Mark Healey by David Smith in January, 2006. It featured a character with a large yellow head, who would later be reincarnated as "Sack boy." The colour scheme of the game (pink, yellow, and blue) was later adopted by the company when painting their offices in Guildford.