Brains is a small transformer drone who originally served the Decepticons before defecting to the Autobots. He was constructed by the Decepticons as a brain unit intended to receive and process a critical data download. However, his creators underestimated his capacity for independent thought, leading to his rebellion and self-adoption of the name Brains. His alternative mode is a laptop computer.

Following the Battle of Chicago, Brains survived the conflict but lost one of his legs in the process. He was subsequently captured by Joshua Joyce and the technology company Kinetic Solutions Incorporated, or KSI. During his captivity, Brains was forced into a form of slavery, compelled to perform mental autopsies on the fallen Decepticons whose remains had been gathered from the Chicago battlefield. His physical condition deteriorated under this captivity, and he was depicted using a makeshift crutch fashioned from pieces of his destroyed leg along with a neck brace.

Despite his eccentric behavior and unusual mannerisms, Brains is essentially a well-intentioned character. He forms a close friendship with Wheelie, another small Decepticon drone who similarly turned to the Autobots. Within the KSI facility, Brains made a discovery of tremendous significance while connected to the head of the Decepticon leader Megatron. He found that Megatron's consciousness was not dead but continued to exist and was actively manipulating KSI from within. Megatron was feeding the company the scientific knowledge and technical specifications needed to construct a new body for himself, which KSI would name Galvatron.

Brains found himself in an impossible situation regarding this knowledge. His captors regularly subjected him to torture whenever he spoke out, which created a powerful disincentive for him to share any warnings. On one occasion, he attempted to reveal the true nature of KSI's work to a visitor named Darcy Tirrel, but Joshua Joyce silenced him with electrocution. The character expresses deep bitterness about his treatment, at one point contrasting the cruelty of human captors unfavorably even with aliens who might simply eat or kill a person.

His situation changed when the Autobots stormed the KSI headquarters. Brains was freed by the Autobot named Hound and subsequently rejoined the Autobot forces alongside their new human allies. Once free, he shared the complete truth about Megatron and the Galvatron plot, explaining that Megatron intended to use a device called the Seed to destroy a major city, convert its matter into transformium, and build a massive army. When questioned why he had not warned the humans at KSI about this danger, Brains responded with sarcasm about the dark place a person goes when confined on death row, suggesting that his torturers had created the very situation that led to their peril. He concluded by mockingly noting that human greed had brought extinction upon humanity itself, a situation he declared was no longer his problem.

Following his rescue, Brains demonstrated a capacity for simple pleasures and relief at his newfound liberty. After delivering his warnings to the Autobots, he departed to enjoy his freedom, shown happily smelling flowers. This moment stands in stark contrast to his earlier ordeal and highlights his resilient yet somewhat cynical personality.

Brains possesses notable analytical and technical abilities. His function as a brain unit grants him significant processing power, and he was able to perform detailed mental autopsies on dead transformers, extracting and understanding complex technical information from their remains. His ability to connect directly to Megatron's head and perceive the still-active consciousness within demonstrates a sophisticated interface capability. His transformation into a laptop computer allows him to be portable and integrate with human technology, though his small size and physical fragility also leave him vulnerable, as evidenced by his lost leg and subsequent captivity.