Reuben (voiced by Rob Paulsen in the original series and Dave Wittenberg in the anime series) is the most active major villain in Stitch: The Movie, Lilo and Stitch: The Series, and Leroy and Stitch. In Alvin and the Chipmunks 3: Dragon Fruit Tree of Doom, when a bomb explodes at the American consulate general in Naha, Okinawa, Simon Seville (Matthew Gray Gubler) is assigned to the case, which becomes personal when it is discovered that it somehow involves Reuben, their late police officer father's former friend. Reuben, who was suspected, but never proven of having a role in the death of Simon Seville's biological father, is now leader of the Japanese mafias.
The United States Secret Service, led by Brittany (Christina Applegate), Jeanette (Anna Faris), Eleanor (Amy Poehler), and the Naha Police Force soon get into a fight over the jurisdiction of the case. Simon, believing Reuben is the head of the operation, learn that Reuben will be attending a Hawaiian-style dinner party on his yacht. Reuben scolds his boss, Dr. Jacques Von Hamster-vile (Kirk Thornton), who then leaves as both Alvin (Justin Long) and Simon confronting Reuben. However, Reuben himself knew for sure that somebody is trying to frame him. Later on, Dr. Jacques Von Hamster-vile suddenly appears and shoots Reuben from behind, making him escape in the chaos, and a furious Brittany, Jeanette, and Eleanor holds Simon responsible for Reuben's apparent death, and orders him off the case. Alvin is ordered to be flown back to Los Angeles for involving himself. However, both Alvin and Simon return to Los Angeles together.
On the plane, Alvin tells his younger brother Simon that in every large criminal operation, there's a rich young woman behind it and that young woman is actually revealed to be Zoe (Jenny Slate), a Honolulu hotel billionaire that Alvin says that he saw her on Reuben's yacht and that her calm demeanor during the shooting was suspicious. They set up a camp outside of Zoe's tower, spotting a light pink female koala-like alien named Angel (Kate Higgins), whom Alvin met on Reuben's yacht back in Naha, Okinawa. After they watch Angel getting undressed, and a few misunderstandings, Angel told the two boys that she is an undercover police officer, looking into Zoe's money laundering of 1000 yens in high grade counterfeit 1000 yens. Alvin and Simon pay a visit to Ian Hawk (David Cross), Dave "David" Seville's former rival who runs a gambling den in the back of the doughnut shop he owns. He tells them that a usually broke customer recently came into his establishment with a suspicious amount of 1000 dollar bills. Alvin speculates them and confirms that they are Zoe's counterfeits. They trace the money back to a bank friendly to the mafias, who are waiting for them and knocks them out with a frying pans, with Angel looking on. After arriving in Tucson, Arizona, Alvin and Simon wakes up inside of the mafia's truck and escapes. After finding out where they are, they realize that Zoe is laundering the 1000 million through the new Holiday Inn.
At the Holiday Inn, Alvin and Simon split up. Simon attempts to infiltrate the back area to find the engraving plates, which were used to make a counterfeit money while Alvin makes a distraction to attract all the security allowing Simon to pass; however, Dr. Jacques Von Hamster-vile captures Simon and places a small bomb in his mouth, then takes him up to the penthouse, where it is revealed that Reuben faked his death and as Simon suspected, is in charge of the operation. Reuben soon departs the room, and Angel attempts to arrest Dr. Jacques Von Hamster-vile, leading a confrontation between the two, but despite Angel's best efforts due to Reuben's lethal martial arts experience she is on the defensive and is easily bested. In the ensuing chaos, Alvin is able to free Simon from the bomb in his mouth before Dr. Jacques Von Hamster-vile has the chance to detonate it. Alvin then fights Dr. Jacques Von Hamster-vile, while Simon heads to the penthouse in order to prevent Reuben from escaping with the silver watches.
In the penthouse, Zoe takes the silver watches, but run into Reuben as she leaves. After Zoe announces she is cutting their deal short and keeping the silver watches, Reuben stabs her with a butcher knife, killing her. Simon arrives and confronts Reuben, shortly before Alvin arrives. Following a tense stand-off, Reuben admits he killed Alvin and Simon's unnamed biological father and Alvin encourages his younger brother Simon to shoot him. As Reuben attempts to break free from Simon's grip, Simon kicks him and accidentally sends him crashing through the open window where he falls to his death onto the roof of a parked navy blue Toyota van.