A member of the crew then handed a bucket and lighter to Paula, prompting the TV host to move away from the mother before she set the bra alight.
"If you don't mind, I'm going to step back. I don't want to burn my hair and stuff. Do you know what I mean? It's expensive!" Karl quipped.
Whether or not Karl was referring to an expensive haircut, or hair implants wasn't clear.
The 45-year-old TV host has been the subject of makeover rumours since his relationship with Jasmine Yarborough, 34, began back in 2016.
In 2017, The Sydney Morning Herald reported that Karl felt "pressure" to remain youthful and as a result, underwent a "subtle hair transplant".