Nimoy is most famous for the role of Spock in Star Trek and might be familiar recently as William Bell in Fringe. This isn't his first foray into the world of Transformers as he voiced Galvatron in Transformers: The Movie.Mr. Spock himself, Leonard Nimoy, has joined the film as the voice of Sentinel Prime, the predecessor of Optimus Prime whose wrecked body is seen in the teaser trailer, found crash-landed on the moon by the Apollo 11 astronauts in 1969. Later, after being brought to earth, he takes the disguise form of a fire engine in the movie’s massive, climactic battle through Chicago.
The idea of Leonard Nimoy returning to the TF universe has been around for a few years now as many fans advocated him voicing a character in Transformers: Revenge of the Fallen. Back in April 2009 Michael Bay was asked about this possibility and he responded, "[Nimoy] is married to Susan Bay, who’s a cousin to me,” Michael explained, saying that he’s afraid of insulting his relative with the mere pittance allotted to pay his voice actors. “I just feel kind of bad about asking him. Like ‘I can’t pay you that much? But would you do this voice?’" This was followed up a week later with Leonard Nimoy himself who simply said that Bay had to just ask.
Apparently has asked and Nimoy has accepted. Even better it seems the character of Sentinel Prime is a rather important one in DOTM so it might just be a few lines like it might have been if Bay had tried to get him for Revenge. EW tends to be right on the mark with their reports but since no one official with the movie is quoted, I have very slight reservations. I hope Bay comments on his forum confirming this news soon. Thanks to GundamFan89, Chris, Sean and Ryan for the heads-up.