Basically, there's the red wiggle, the blue wiggle, the purple wiggle, the yellow wiggle, the fifth & first wiggle, the fill-in yellow wiggle <breath> the original red wiggle, the original purple wiggle, and the chick with the bow.
I eventually remembered that there's now a new generation of this popular group of children's entertainers. I gather the chick ("Emma" as she's also known) is a favourite among many little girls.
Quarter by quarter, I iced the cake with the various Wiggles colours (matching the design of the Big Red Car's wheels). Wondering how I was going to get the edges straight, I found it helpful to pipe the outline, and then fill it all in. It was as straight as it was going to get.
Once it was all iced with Wiggles colours, I unstuck the Wiggles photo and placed it in the middle of the cake. Now it was complete! That was until...
I stuck that onto the yellow section of the cake, and now it was finished: