Another four part arc featuring Darth Maul was written for the following season, but never completed when the Clone Wars was canceled. It was adapted into a four part comic book series by Dark Horse titled 'Darth Maul: Son of Dathomir'.
Upon sensing Sidious's approach, Maul utters "I sense a presence. A presence I've not felt since..." This is, of course, the line from episode IV, A New Hope, spoken by Darth Vader upon sensing Obi-Wan's approach, on the first Death Star.
Second appearance of Tim Curry as Chancellor Palpatine/Darth Sidious. Like his first appearance in "Revival" S5E1 he is uncredited for a single line of dialogue. Curry replaced Ian Abercrombie after his death and voices Palpatine/Sidious until the end of the series.