Lambo is a young hitman from the Bovino Family who is first introduced when he travels to Japan with the intention of killing the famous hitman Reborn in order to prove himself worthy of leading his own mafia family. He is five years old at the start of the series and comes from Italy. His appearance is distinctive, as he dresses in a cow suit with a tail and has a large afro with horns on the sides of his head, giving him the look of a bison. Despite his bold claim of being the great Lambo-san, he is in truth a complete crybaby who often panics and bursts into tears when faced with difficulty. His emotional vulnerability contrasts humorously with his ambition, which is to one day rule the world. He often uses the phrase gotta stay calm right before resorting to a desperate measure.

Lambo carries a weapon known as the Ten-Year Bazooka, a device from the Bovino Family that swaps the user with their self from ten years in the future for a period of five minutes. Whenever he loses his composure, he typically shoots himself with the bazooka and is replaced by his fifteen-year-old self. This older version of Lambo wears a casual suit and a cow-print shirt, but despite being more physically mature and handsome, he remains just as timid and prone to complaining. His speech often begins with a phrase meaning oh my, and he frequently mentions a future involving menial tasks such as cleaning toilets. If the fifteen-year-old Lambo also uses the Ten-Year Bazooka, the twenty-five-year-old version appears. This older self is far more disciplined, intelligent, and powerful, capable of fighting effectively, though the five-minute time limit often cuts his appearances short.

After failing to kill Reborn, Lambo ends up living in the same house as Tsunayoshi Sawada, the candidate for the Vongola Family boss, and forms a close bond with Tsuna's mother, Nana, whom he grows very fond of. Over time, Tsuna becomes a caretaker figure for him. Lambo is eventually chosen by Iemitsu Sawada to serve as Tsuna's Guardian of Lightning, one of the six Vongola guardians. This marks a significant shift in his role from a comedic intruder to a member of the Vongola inner circle. He participates in major story arcs such as the Varia conflict, where he faces the Varia lightning guardian Leviathan. During that battle, the five-year-old Lambo struggles badly, then uses the Ten-Year Bazooka to call his fifteen-year-old self, who is also easily defeated, and then again to summon the twenty-five-year-old version, who nearly defeats Leviathan before the time limit expires. He is saved from a fatal blow when Tsuna intervenes. Later, during the Future Arc, Lambo is transported to a dystopian future where the Vongola are nearly wiped out. He joins Tsuna and the others in infiltrating the Melone Base and receives training from Hayato Gokudera in the use of rings and boxes. In the Inheritance Ceremony arc, he fights against Rauji of the Shimon Family; his desire to simply play with Rauji provides the flame energy needed to form his Vongola Gear, the Vongola Helmet Ver. X, which allows him to defeat Rauji with the Ironhorn Electrico attack.

Lambo's key relationships include his one-sided rivalry with Reborn, who always outmatches him; his affectionate bond with Nana Sawada; his reliance on Tsuna for protection and reassurance; and his companionship with I-pin and Haru, who often take care of him. He is frequently teased or bullied by Gokudera, who has written the words stupid cow on his horn. His relationships with the other Vongola guardians are generally friendly but often comedic, as they treat him like a child, which he is.

In terms of abilities, Lambo has a natural resistance to electricity due to a condition called Electric Skin, which allows lightning to pass harmlessly through his body. In his five-year-old form, this is his only notable power, and he often relies on hand grenades and other explosives that frequently backfire on himself. When he grows older, he develops offensive techniques. The fifteen-year-old Lambo can use Thunder Set to summon lightning and charge it through his body, followed by Electrico Cornata, which channels lightning into his horns for a shocking melee attack, though it is short-ranged and easy to avoid. The twenty-five-year-old Lambo perfects these abilities, creating Perfect Electric Skin to make himself immune to all forms of electricity, Electrico Reverse to gather and redirect lightning, and an extended version of Electrico Cornata that shapes the electricity into a blade to overcome the short range limitation. During the Future Arc, he gains a Vongola Box weapon called Gyuudon, a lightning bull that he can ride, and Lampo's Shield, body armor that emits powerful electrical bursts known as Corna Fulmine. Later, his Vongola Ring is remodeled into the Vongola Helmet Ver. X, a set of full body armor with electrified horns. Despite his frequent comic failures, Lambo demonstrates growth throughout the series, evolving from a useless crybaby into a more capable ally who can hold his own in battle, especially when his older selves are summoned. His character remains a blend of childlike innocence, comedic cowardice, and occasional flashes of real bravery.