They "are bigger and badder-ass than they have ever been," says Lorenzo di Bonaventura, who has produced all four films, with Steven Spielberg and Bay as executive producers.
"Michael (Bay) has always been conscientious about the need to keep topping 'the last one.' First it was topping the animated Transformers television program, now we need to top our third movie," says Di Bonaventura.
Bay says the "new chapter" required refreshing the look. "A lot of people are like, 'What does that mean, Transformers 4?' It's like Batman with a new suit. We needed to change the look from top to bottom."
"The sword is emblematic of what we've done to Optimus Prime as a whole," says Di Bonaventura. "He's been upgraded with more abilities."
Bumblebee takes his martial arts to another level with Chinese star-style adornments on his armor. The two also have new souped-up transformation vehicles. Optimus Prime eventually reveals himself "like a knight in shining armor" as an impressive Great Western truck, says Di Bonaventura. Bumblebee re-emerges as a new souped-up Camaro. Yellow, naturally.
The upgrades continue with the introduction of Dinobots, ancient creatures who enter the franchise "with their fists and feet first," says Di Bonaventura.
The biggest difference in Extinction is that humans are fearful and less trusting of both heroic Autobots and evil Decepticons since the Transformer destruction of the last film. After devoting himself to protecting humans, Optimus Prime turns hard and cynical about this human betrayal.
"There are changes, but he still maintains the element of characters that are so important to him," says Peter Cullen, who has voiced Optimus Prime in each movie since 2007's Transformers and in the 1984-1987 TV series. "Since the original concept of Optimus Prime, the trustworthiness, the honor, the courage are still there. That will always prevail. And that's the basis of his popularity."