Zardo Zap is an alien played by Niki Owen in the title of the episode. In Toot Toot! and Communication, she's also played by Leanne Halloran in the title of the song and Elyssa Dawson in Let's Have a Ceili.
The Wiggles and Zardo Zap
Zardo Zap in "Toot Toot!" played by Leanne Halloran
Zardo Zap and Elyssa Dawson
Elyssa Dawson as Zardo Zap
Officer Beaples and Zardo Zap
Zardo and the kids in "Communication"