Near the end of "To Catch a Jedi," Barriss Offee (whose identity isn't revealed until the next episode) steals Asajj Ventress's mask and lightsabers and, disguised as Ventress, attacks Ahsoka Tano. During the fight, she slashes a pipe so that the resulting exhaust temporarily stuns Ahsoka.
While this is somewhat similar to an event in The Empire Strikes Back, where Luke directs exhaust from a cut hose in the carbon freezing chamber at Vader, creating enough of a distraction so that he can retrieve his fallen lightsaber, it actually has a closer analogue in an earlier episode of The Clone Wars, and this holds greater significance.
In "Cloak of Darkness" (S1E9), there's a lightsaber duel between Luminara Unduli and Asajj Ventress in which Ventress does the same thing: she cuts a pipe in the Jedi cruiser so that the steam compromises Luminara's vision. Ahsoka was present at the duel (albeit the later stages), and since Barriss is Luminara's padawan, it's likely that she's familiar with it, too. In "To Catch a Jedi," she adopts this move as an-other facet of her disguise and an-other way to make Ahsoka believe that she is Ventress.