He's introduced early on as a devoted fan of Benibara Otome, an Earth TV drama centered on the character Beniko. His fandom is genuine—when he watched a scene where Beniko was in danger, he got so worked up that he actually tried to mount a rescue mission on Earth, not fully grasping that he was watching fiction (Jumba and Pleakley eventually explained the TV concept to him in episode 14). By the series finale, hearing Beniko's voice on a recorded cassette tape sent him into overdrive, and he seriously chased down Pleakley when the latter dressed up as Beniko—a moment that really drives home how much a fan he actually is.
Pleakley, it's worth noting, wasn't into the show itself but got pulled into it through Earth cosplay culture. He'd even ordered the Narikiri Beniko-ojousama Set by mail, which happened to be the same costume kit that Gantu received as a Christmas gift from Reuben in episode 13.
He's carried over a few quirks from earlier appearances: he sings badly and has this thing for ship captains. In the third series, he takes a lot of heat for botched missions, often getting punished alongside Dr. Hämsterviel. He occasionally mentions being a former Galactic Federation commander, suggesting he either retired or got fired again after being rehired—probably connected to whatever went down with Leroy during that series.
Content compiled by AnimeList.moe from publicly available sources.