Leela's Wrist Thingy

Strapped to Leela's arm, this device is technically just a wrist-mounted computer, but Futurama gives it a voice, an attitude, and occasional opinions about the situations Leela drags it into. It answers questions, relays information, and reacts to danger with the mild exasperation of a gadget that expected a calmer job.

The joke is the confidence: nobody explains why the wrist thingy talks, it just does, and Tress MacNeille plays it with the same deadpan competence she brings to the show's other odd corners. It's a small, disposable-seeming gag that Futurama trusts completely, which is exactly why it lands.