I'll tweak David's suggestion a bit and put forth
Megnificent as a nickname for Megan.
But now that we've had a few days to process the exciting news that the Megnificent Megan Walsh has joined Celtic Woman, it's time to come up for a nickname for her fans (or find an existing one, if you can).
Celtic Woman fans have found some really creative ways of naming themselves over the years. To name a few:
Meaviacs
Sharpies
McManiacs / McMahoniacs / McFans
Lisaholics
Chlovers
There were some decent ones that never caught on but probably should have, like:
Nesbuds
Mermaireads
Fallon's Followers
Shanfans
Lisa's Lamb's / Lisa's Lambe's
Taradactyl's (lol, I liked it)
Now, it's time for us to add to the tradition!