Creator Backlash: After ROTF had been out a while many people involved with it admitted that it wasn't the movie they were hoping it would be, Michael Bay included.
Executive Meddling: You might be wondering why the name of the college Sam Witwicky went to is not named. That's because after filming both Princeton and the University of Pennsylvania, the colleges forbade Michael Bay from revealing the name of the college after they filmed a scene where Mrs. Witwicky got accidentially high on pot brownies and went around campus in a pot-induced humiliation fest.
Promoted Fanboy: Josh Nizzi created a fan design for a movie-based Long Haul, which was so good he was brought to Hasbro and eventually to the actual film production team. In addition to Long Haul being the first new design approved for ROTF, he ended up designing Jetfire, the new Megatron and Powered-Up Optimus Prime.
Viral Marketing: Rival conspiracy websites mentioned in the film reallyexist. However, neither TheRealEffingDeal.com nor GiantEffingRobots.com are around anymore as of 2018 (or possibly even earlier).
What Could Have Been: There can be a very interesting book written about how a number of factors made this movie the (debated) low point of the franchise.
A TON of ideas got scrapped, some late in the game, including:
Arcee being a combiner who would regularly take on a merged form that was roughly Bumblebee's height. This was dropped so late that the two of the three toys for Arcee retained this ability.
Skids and Mudflap being able to combine.
Sideways was supposed to have a larger role but Audi chickened out, causing them to give much of his scenes to Demolisher... only for Audi to change their minds BACK to having him in the movie, resulting in his quick scene.
Fan favorite Springer was scheduled to be in the movie as an Osprey twin rotor helicopter, with two toys released based on the design. The guess is he was dropped because the Osprey design would make him absolutely tower over near every other robot (at about 60 feet tall) and give Devastator a run for his money.
Several Seekers were slated to appear, including Ransack. Again, got toys because of them being deleted so late in production.
Soundwave would have gained an earth alt mode, namely a Chevy truck.
Originally the Fallen was supposed to be trapped in an alternate dimension of sorts and only able to escape when all the Primes were gone, rather than just hanging out in his ship.
Sam was supposed to transfer all the knowledge he gained from the Allspark to the Matrix, which in turn would become a new Allspark for the Autobots.
The various adaptations feature a different ending than the movie itself, where Megatron, having found out that The Fallen had been lying to him and manipulating him all this time, leaves his master to die and flies back to the Nemesis with Starscream to awaken his new army.
James Arnold Taylor was originally cast as the Fallen, but was later replaced by Tony Todd. He did keep the role for the video game though.