In IDW Publishing's crossover comic combining Transformers and Back to the Future, one of Hill Valley’s iconic landmarks is revealed to be a Decepticon. The famous Clock Tower has been a staple of the Back to the Future franchise ever since the historic bolt of lightning that struck it back in 1955 helped send Marty McFly back to his home in 1985. While Marty and the faithful yet eccentric Doc Brown try to repair the timeline in Transformers/Back to the Future, they learn that some things truly are more than meets the eye as the Clock Tower surprises everyone by transforming into a gigantic Decepticon.
In Transformers/Back to the Future, members of the Decepticons witness the events at the beginning and end of Back to the Future and seek to use this to their advantage in their war with the Autobots over Earth. Marty wakes up to find the world vastly different than the one he remembers, with humans living in ruins while they're forced to work tirelessly for the Decepticons. With the help of a Transformer called Gigawatt, Marty learns a Decepticon named Rumble hitched a ride with Doc Brown to 2015 and, under the guise of friendship, helped Emmett repair the damaged DeLorean. Once the time-traveling car is repaired, Rumble betrays Doc Brown, traveling back in time. Rumble awakens Megatron earlier than before, which allows the Decepticon leader to kill his nemesis Optimus Prime, ensuring the surviving Autobots are not strong enough to stop the Decepticon takeover of Earth.
In Transformers/Back to the Future #3-4 by Cavan Scott and Juan Samu, Marty and Gigawatt search for Doc Brown, who is resisting the Decepticons' rule of Earth, hoping to redeem himself for his hand in wrecking humanity. With the few remaining Autobots, Marty, Doc, and Gigawatt reunite with Marty's parents and help to score a crucial victory in this warped version of 2015. While Marty boasts there are no more Decepticons to fight, everyone learns that a colossal Decepticon has been sitting there in plain sight the entire time. Towering over everything and armed with an impressive armada of blasters and weapons, the famous Hill Valley Clock Tower and Courthouse reveals itself to be a Transformer.
The Clock Tower has played an important role in the Back to the Future trilogy. It was its famous lightning bolt which helped Marty return home, people were still trying to raise funds to keep it standing in 2015, and the series' duo were even present as it was being constructed, Marty narrowly avoiding being hanged in front of it in 1885 (a stunt that nearly killed star Michael Fox.) It was therefore always necessary for Transformer/Back to the Future to do something fun with the building, but revealing it as a towering threat was still a huge surprise. While the surviving Autobots fight the mechanical gargantuan, this Clock Tower Decepticon makes it clear the evil Cybertronians will not give up this new timeline easily. Doc and Marty hope to use Gigawatt to go back in time and stop Rumble's interference, even as Bumblebee and Rodimus Prime, Optimus' son, are killed in battle.
When the Clock Tower damages Gigawatt, it would appear the clock has finally run out for the series' time-traveling protagonists. But fortunately Doc and one of the last remaining Autobots help push Marty and the transforming DeLorean to 88mph, hoping their sacrifice will allow history to be corrected or at least modified into something better. Fans might have thought there were few iconic new Transformers to mine from Back to the Future, but they'd have been wrong, as both the DeLorean and the Clock Tower take on awesome new forms. While Marty and his Transformers allies are successful, the crossover's ending suggests that Back to the Future's role in future Autobot vs Decepticon conflicts may be far from over, creating the possibility that some new future may see the Clock Tower Decepticon return!