Also, Australia has Mardi Gras, too?

It's the big annual gay pride march in Sydney: https://en.wikipedia.org/wiki/Sydney_Gay_and_Lesbian_Mardi_Gras

They use the name 'Mardi Gras' because at the time of the first one it was just synonymous with a street festival of any kind.

But Mardi Gras originated as a Christian celebration (also known as Shrove Tuesday) before Lent, so a lot of places have a Mardi Gras celebration connected to that tradition: https://en.wikipedia.org/wiki/Mardi_Gras