Denny Clay is the owner and proprietor of the Vintage Salvage Depot for the Discriminating Nostalgist, a sprawling scrapyard located just outside Crown City. To most people, his collection appears to be little more than junk, but Denny is a consummate collector who believes his eclectic assortment of memorabilia and antiques will someday be worth a fortune. He lives up to the saying that growing old does not necessarily mean growing up, as he demonstrates a youthful, sometimes childlike enthusiasm for his interests, including a fondness for cheesy glam-rock music and a past fascination with professional wrestling that continued until he learned it was scripted. Denny wears his heart on his sleeve and often comes across as less mature than his own son, Russell.

Despite his eccentric and sometimes immature personality, Denny is a major asset to the Autobot team that takes up residence in his scrapyard following the crash of the prison ship Alchemor. He provides the Autobots with a place to operate, a cover story, and a base of operations. His natural know-how for mechanical work allows him to assist the Autobot Mini-Con Fixit in repairing and understanding Cybertronian technology. Denny is more than ready to bend the rules and break a few harmless laws to help keep the presence of the Cybertronians on Earth a secret. He is quick with a disguise and a fake name, often the same one, to distract local authorities and maintain the Autobots' cover. On several occasions, he has posed as a noted archaeologist or a safety inspector to help the team gain access to locations where Decepticons have been spotted. His childlike manner and experience as a father also allow him to offer valuable advice, helping the young and inexperienced Autobot leader, Bumblebee, deal with his team's personal problems.

Denny's primary motivation is to help the Autobots in their mission to recapture the escaped Decepticon prisoners while also keeping his son, Russell, safe. In the beginning, he is eager to assist but can be somewhat clumsy and accident-prone, but he quickly proves his bravery and resourcefulness. He personally participates in missions, using his construction equipment to battle Decepticons or to extract the Autobots from dangerous situations. When the bounty hunter Fracture targets Bumblebee's team, Denny is kidnapped, which initially leads him to decide that Russell should no longer accompany the Autobots on missions. However, he soon changes his mind, recognizing his son's capability and the importance of their shared cause. His relationship with Fixit is particularly notable; although the two occasionally clash due to Denny's desire to be more involved with the technical work, they ultimately form a strong and effective partnership.

Throughout the series, Denny develops from a well-meaning but sometimes hapless collector into a confident and indispensable member of the Autobot team. He and Russell regularly fight alongside the Autobots to defend their scrapyard home from Decepticon invasions, using the yard's resources and their own ingenuity to hold their own against much larger foes. In one instance, Denny even manages to knock the powerful Decepticon Soundwave back into the Shadowzone using his crane. While his collection of junk is frequently damaged or destroyed during these battles, Denny's resolve never wavers, and he continually demonstrates that his value to the team lies not in his possessions but in his heart, courage, and unique skills as a mechanic and a human ally to the Autobots.