The episode: “Space Mutiny,” ep. 820
The riff: Exclaimed under his breath (I know that sounds like an oxymoron) by Tom as the ship’s second in command gives an impassioned address to the captain, telling him they need to fight back against the mutineers.
The explanation: Throughout the episode, Mike and the Bots make fun of the second in command by saying “Oi!,” in reference to a series of Energizer battery ads from the 1980s featuring Australian football player Mark “Jacko” Jackson. “Strewth” is another term with meaning in Australia, although it seems to mean something slightly different in the U.K. In British parlance, it’s short for “It’s God’s truth,” a form of agreement. In Australia, though, it’s more of a general exclamation of surprise, similar to the better known “crikey!”
Novelty factor: I was sort of familiar with the term (I remember reading it in “John Constantine: Hellblazer” comics), but I don’t think I’d ever looked up the definition before.