The later parts will go over the other characters. I should let you guys know that Hasbro(the company that runs Transformers) has recycle character names. You can see a character in the Unicron Trilogy or Animated that has the exact name as a G1 character but there is barely a resemblance to the G1 character. It doesn't mean they're a re-imagined character, they're simple a name that Hasbro has a copyright to and recycle the name. This was common before and after the TF movies. Half the cast in the movies were simply original characters whose name was reused from an earlier source.
The 2007 Autobot cast is Optimus, Bumblebee, Ratchet, Ironhide and Jazz. These are well known G1 characters and their personalities are similar.
Believe it or not, the 2007 movie was actually the closest we got to G1 at the time. All the other shows at the time mainly had Optimus, Megatron, Starscream, and a whole bunch of original characters. There may of been one or two that was a re-imagined character, but for the most part, it's a cast of orginals. So yes, a Micheal Bay movie was the most faithfully to G1 at the time. Otherwise the cast be Optimus, Hot Shot, Red Alert, Rhinox, and Rapid Run.
Now for the 2nd movie Autobots, starting with is the three Acrees.
Acree is based on the token female good bot of the original show. She was intended to be in 1st movie as a single character but scrapped late in development. She reappeared with two others. Some say she's one bot whose conscience is split into three. Others say it's three separate bots who mind were linked due to an experiment.
There's Sideswipe. Sideswipe was the cool lambo in G1 with little screentime to the cool car on roller skates with little screentime.
Wheelie was an annoying rhymer in G1, who have no resemblance to Megan Fox's leg humper. G1 Wheelie was the most hated character at the time. So this horny guy is kinda of an upgrade.
One character is Jolt. For those wonder who Jolt was, he was the guy that help Optimus and Jetfire combine at the end of the movie.
This is all you see of Jolt in the entire movie. He didn't even have a line.
The idea of Jetfire and Optimus combining is actually from the 2002-03 series called Armada.(The Jetfire in that series is also different from G1)
Their combined form
The twins were original characters that Micheal Bay made up. So yes, you guys can blame it on him. Skids and Mudflap are actual reused names from previous series but that doesn't matter.
Discussing the 3rd movie now. The Autobots have Que, Dino, and the Wreckers.
The Wreckers(the Nascars) are a special forces/commando unit in the comics. In the movies, they got beer bellies, caps, mullets, and sunglasses. Yes, they were designed to look like the stereotype of Nascar fans.
Que/Wheeljack
Dino/Mirage
Que and Dino are sort of G1 characters. They were called Wheeljack and Mirage in development but a last minute change cause their names to be changed. Que/Wheeljack is the inventor of the group which is fitting but they made him look like Einstein. Dino/Mirage didn't have a Italian accent in G1.
This is Brains and he isn't based on anyone.
Now with the 4th movie, Crosshairs is originally made character. There's technically a G1 character with the same name but it's a very lesser known one and from what little I know of him, he's not really connected to this guy.
Hound is in G1 and he was a nature lover army jeep. In the movie, he is an overweight cigar smoking redneck voice by John Goodman. Big difference there.
Drift, the samurai bot is technically a G1 character, just not from the 80s. He was made in the late 2000s in the comics.
G1 Drift wields samurai blades and has colors of the rising sun. I don't think you can accuse Bay on this one for making ethnic stereotypes
The Dinobots are a popular group of characters. They are the Autobot's muscle. In some versions, they are the dumb comic relief. In others, they oppose Optimus' rules and make their own when battling Decepticons. Sadly they don't show up till the last 10 minutes of the 4th movie and they have even less screentime in the 5th one.
Now the 5th movie
Hot Rod is this young punk kid with end's up with Optimus' Matrix and turns into Rodimus Prime and becomes the leader of the Autobots after Optimus' passing,...or until Optimus comes back from the dead next season.
The movie's version gives him a French accent and he's not a major character in any sort of way. I seriously doubt he's going to be the leader of the Autobots.
This Ninja Robo Butler named Cogman is an original character. He's says he's a Headmaster. Basically he transforms into a head that connects to a Transformers body.
Sqweeks is an original character.
