Dexter (known as Megane-kun in Japanese) is a hamster sporting distinctive tan fur markings around his eyes that resemble glasses. He resides in a glasses store owned by his human, the optometrist Curtis. Dexter presents a refined, well-mannered, and intelligent persona, often wearing a red bowtie. He demonstrates his intellect through actions like proposing to create a Latin motto for the Ham-Ham Clubhouse.

His primary dynamic involves a long-standing rivalry with his best friend, Howdy. Both compete for the affection of Pashmina, frequently arguing over Howdy's jokes or Pashmina's perceived interest. Despite this rivalry, a deep friendship endures beneath the surface. They show mutual protection and reconciliation during challenges. Their human owners, Curtis and Howdy's owner Goldie, share a similar dynamic. Pashmina typically ignores or mediates their conflicts, displaying no romantic interest in either hamster.

In the spin-off *Tottoko Hamutaro Haai!*, Dexter features in episodes centered on his relationship with Howdy. These include an argument sparked during a cleaning task and another episode where they compete to accompany Pashmina to a flower field. Further arguments between them sometimes require intervention from Boss.

Dexter also experiences a brief admiration from Hannah, who finds him sweet and sophisticated. This infatuation ends quickly after Dexter becomes queasy on an amusement park ride, leading Hannah to deem him a wimp. His role consistently portrays an intelligent, somewhat fastidious hamster engaged in a comedic rivalry.