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I HIGHLY doubt that those working with the movie gave even a tiny bit of thought about the fact that Energon Superion's limbs resembled A-10 Warthogs. At very most, they likely chose the vehicles first, and later on eventually said "Hey, there's a Transformer of this guy. Cool."
I have to disagree with you. When people are making and producing videos, they put more into the movie than their name in the credits.
Obvious example: the 217 in Sam's eBay name is Bay's birthday (Feb 17). That was not a coincidence. That was planned.
Not so obvious example ("Herbie Fully Loaded"): Maggie (Lohan) pays $75 for Herbie. Jim Douglas (Dean Jones) paid $75 for Herbie in the first flick.
Here's another one: (Final Fantasy Advent Children): Cloud's original Buster Sword that's stuck in the ground overlooking Midgar is the spot where Zack (the person Cloud emulates during FF7) was killed. The Buster Sword is the sword Cloud took from Zack after the death. (Yep, took it right off IMDB. Sue me.)
The point I'm trying to make is that nothing in movies happens by accident. There is not a doubt in my mind that people from Hasbro, Dreamworks, Spielberg, The US Military, et al, had a powwow one day to discuss what vehicles-turned-TFs could be placed in the movie. It's the little things that are worked into the film that makes a movie that much more satisfying to watch.
And when all the kiddies watching the movie for the 100th time go to play with their TFs, look at one of them and realize it was in the movie, there's no greater sense of "Wow! Cool!"
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Calling them cameos or even references are misleading, though.
Cameos are simply acknowledgments to something because it means something to where the cameo appeared. In this case, cameo appearances from previous TransFormers toy lines are quite justified in a TransFormers movie.