Most of the voice cast from the original 80s Transformers show and its movie reprise their roles, some of them after decades, including Peter Cullen (Optimus Prime), Frank Welker (Megatron and Soundwave), Dan Gilvezan (Bumblebee), Michael Bell (Sideswipe and Scrapper), and Gregg Berger (Grimlock and Long Haul) among others.
Contributed by PirateGoofy
The developers at Platinum Games, who were huge Transformers fans since childhood, decided on the Generation 1 aesthetic of this game. In order to modernize it, in addition to the 80s G1 cartoon, they also took inspiration from the G1-themed Transformers comics by IDW as well as the Transformer: Generations toyline, which is also based on the original 80s designs.
Contributed by PirateGoofy
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Several signs in the game contain Easter Eggs that reference different names and other things from the original series or Generation 1 themed Transformers lore and media. A few examples are:

•"Maccadam's Vintage Oil" - A reference to a place on Planet Cybertron, equivalent to an Earth Bar, where Transformers can consume recuperating oil and that was also known as a non-conflict-zone during the Cybertronian war.

•"Bahoudin's" - An homage to the "Pearl of Bahoudin", a powerful MacGuffin from a storyline in the first Transformers animated series.

•"S. Witwicky" - A callout to Spike Witwicky, the young human protagonist from the same show, and his father Sparkplug.

•"Lander's Beverages" - a rather deep cut to one of the lead characters in the "Super God Masterforce" anime, a TV show that acted as somewhat of a sequel to the G1 cartoon that was only aired in Japan and featured "Pretenders" (such as Lander), which are Transformers that can take human form, among other things.
Contributed by PirateGoofy
There are a series of Transformers: Devastation PlayStation 4 faceplates that were only released in Japan and in a limited number, despite the game getting no Japanese release.
Contributed by PirateGoofy
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Decepticon Cassette Ratbat was going to appear in the game, but was cut prior to release. He has a full model rendered in the game's data.
Contributed by PirateGoofy