20 Things You Didn't Know About Transformers
18. Liam Neeson Served As The Inspiration For Prime's Body Language
All fully CGI characters need a reference point if they are not assisted by motion capture. For Optimus Prime, leader of the Autobots, the animators at ILM (Industrial Lights & Magic), they found their reference point in famous Irish actor Liam Neeson.
This wasn't just because Bay believed Neeson's movement were worth looking at, it is actually because Bay initially intended for him to voice the character. This information comes courtesy of the directors commentary, where he also reveals that the producers pushed back against this idea and they requested he consider the original voice actor, Peter Cullen.
Bay decided to test Cullen against the new CGI model of the character and came to the conclusion that no one else could voice him. Neeson, instead of being the voice, became a reference point.
A similar reference technique was used in the third film in the series, Transformers: Dark of the Moon, where Prime's mentor, Sentinel Prime, has his face modelled after Sean Connery.