Luca first appeared as a tiny alien hiding away from several MIB agents in 1996. He took refuge in a Brooklyn apartment, where he is spotted by a little girl named Molly Wright, who helped Luca escape while witnessing her parents being neuralyzed by the agents.
Because of this event, Luca felt grateful towards Molly and worked his way up in the criminal underworld for the next 23 years, eventually growing himself up to become the second-in-command of Riza in selling alien weapons on the black market.
Following Molly's new job as a MIB agent (now going by "Agent M") and being tasked with her partner, Agent H, they were told of a certain crystal given by Vungus the Ugly (who was killed by the Twins on the orders of High-T) that is actually a weapon powered by a compressed blue giant. However, H's alien contact stole the weapon and delivered it to Riza, who intends to sell it on the black market for a good fortune.
Heading over Riza's island fortress, both agents (along with their new alien friend Pawny) managed to take down Riza's men and attempted to infiltrate the base and recover the weapon, but they are caught by Riza and Luca. While Riza was able to take down Agent M, Luca managed to take down Agent H. However, upon learning that Luca was a Terrantian (and remembering her experience as a kid), Agent M recited the phrase, "Kabla nakshulin." Luca questions where M could've learned, and she explains how she had met a Terrantian when she was a kid and how she had helped the little creature. Hearing Agent M's story, Luca soon realizes that Agent M is the same little girl who had helped him escape the MiB-agents when they first met.
Gratefully to Molly for helping him escape that first time, Luca turns on Riza and forces her (at gunpoint) to give the weapon to Agent M and allowing her, Agent H and Pawny to escape. Before leaving, Agent M asks Luca what "kabla nakshulin" means, and he says that it means, "I'll kill whoever you choose in the most gruesome way imaginable." Hearing this, Agent M asks Luca to keep Riza alive (for now at least).
It is unknown what has happened to Luca afterwards, as he was not seen or heard from again following the deaths of High-T and the Twins.