There are many Easter eggs in the game, some can be found in certain levels of the game. Addionally between loading screens there are quotes from Generation one.
As part of the G1 Retro DLC pack, Players can play multi-player games with a playable skin of Generation 1 Optimus Prime as well as unlock 2 weapons designed after Generation 1 Megatron in Blaster form and Shockwave's Generation 1 Laser Cannon. Both weapons make the iconic "Transforming" sound from the 80's Transformers cartoon.
When Megatron is in Soundwave's old workshop, you can see Frenzy jumping over junk on a treadmill.
During Level 3, Soundwave can be seen with Laserbeak after transforming from his Iconic Cybertronian lamppost Alt Mode. Listen for the shrieks.