The company even met with Valve, which suggested the two work on the game together.
"We were very tempted," studio co-founder Alex Evans told Kikizo. "But in the end we decided to talk to Sony and they just got the game at the beginning."
Media Molecule had previously worked with Valve for the Steam release of its physics-driven action game Rag Doll Kung Fu.
Developed internally at Valve, Portal (PC, PS3, 360) and its wit-driven take on puzzle-action shooting was released last fall to critical acclaim. It was inspired by the 2005 independent game Narbacular Drop, the creators of which are now at Valve.
LittleBigPlanet, originally unveiled in early 2007 as part of Sony's Game Developers Conference presentation, is slated arrive on October 21 as a PS3 exclusive.