I suspect you will get some different responses once the Australians who participate on this board find the thread.
"Meegan" is evidently the way that
Megan is pronounced by the huge majority of Australians. I suspect that Australian Megans who move to the USA are often tempted to respell it as Meegan to get people to pronounce it the way they prefer.
And in Australia they probably think the way most Americans pronounce
Megan is "weird". :)