"Transformers: Age of Extinction," the fourth film in Michael Bay's CGI-packed series, includes a lot of new faces -- both human and non-human alike. Click through our character guide for a refresher.
Optimus Prime is the leader of the Autobots, the benevolent faction of the Transformers who initially protected Earth from the villainous Decepticons. Following the destruction of Chicago in 2011's "Dark of the Moon," the Autobots have had to go into hiding after humanity launched a full scale attack on all Transformers. At the beginning of "Age of Extinction," Optimus Prime is seen posing as a beat-up semi-truck purchased by Mark Wahlberg's character, Cade.
Grimlock is one of the main Dinobots featured in "Age of Extinction." He can transform into a fire-breathing T-Rex reminiscent of Godzilla. Optimus Prime is seen using Grimlock as a mode of transportation during the film.
Voiced by Mark Ryan, Lockdown is one of the film's main villains and stands out as a Transformer who is neither a member of the Autobots or the Decepticons. He is a cunning bounty hunter whose loyalties lie only with the highest bidder. He was mysteriously sent to Earth by an anonymous client to capture one of the Transformers. Lockdown can transform into a 2013 Lamborghini Aventador sports car.
Hound makes his big-screen debut in "Age of Extinction," here voiced by John Goodman. His look in the film has changed compared with his appearance in the 1980s animated series. He know sports a beard and is seen using a bullet as a cigar. Hound can transform into a Oshkosh Defense Medium Tactical Vehicle.
After the Battle of Chicago, the severed head of Megatron (leader of the Decepticons) was taken by Joshua Joyce's (Stanley Tucci) tech firm KSI and placed on a new body to create Galvatron, one of Optimus Prime's greatest foes. Voiced by Frank Welker, Galvatron has the ability to transform into a 2014 Freightliner Argosy cab-over semi-truck.
Bumblebee is a member of the Autobots and one of the smallest Transformers of the group. He turns into both a 1967 and 2014 yellow Camaro in the film. His voice module was destroyed, leaving him able to communicate only through playing songs and soundbites on his radio. He is carried around by the Autobot Strafe.
Like Galvatron, Stinger is a man-made Transformer and belongs to the Decepticons. He is usually thought of as a foil to Bumblebee. In the film, he can transform into a 2013 Pagani Huayra sports car.
Voiced by John DiMaggio, Crosshairs is the weapons expert among the Autobots. Unlike some other members of his faction, Crosshairs is not a huge fan of living on Earth. He can turn into a 2014 Chevrolet C7 Corvette Stingray and is paired up with the Dinobot Scorn.
Scorn perhaps causes the most destruction among the Dinobots. He can transform into a Spinosaurus.
Drift is on the Autobots team and is voiced by Ken Watanabe. He can transform into a 2013 Bugatti Veyron Grand Sport Vitesse sports car. He is often seen with the Dinobot Slug.
Like Drift, Brains was also a former member of the Decepticon before transferring over to Autobots. He is under human captivity for much of the film. Brains has the ability to turn into a laptop.
Newcomer to the series Mark Wahlberg plays the film's lead human character, Cade Yeager -- a cash-strapped mechanic and inventor from Texas who hopes to sell the scrapes of an old truck to pay his daugther's (Nicola Peltz) tuition. He reluctantly joins forces with his daughter's boyfriend, Shane (Jack Reynor), when they find themselves on the run from government forces who want to destroy all Transformers, including Optimus Prime.
Kelsey Grammer -- Harold Attinger
The former "Frasier" star plays the film's main villain, government agent Harold Attinger, who will stop anyone in his way of carrying out his mission to wipe all Transformers off the planet.
Tucci steps into the role of business tycoon Joshua Joyce, who wants to build his own line of Transformers using the unstable metal Transformium. His ambitions blind him from seeing the dangers of his endeavors.