M.O.O.N spells Holly.
 

I wasn't too sure about Holly after her debasement at the hands of Keith Lemon, but I think she works here as Dec's retarded sister. The show improves A LOT when you enjoy her efforts that way.
Also, what is a John Barrowman? Is he essentially a fat, gay, American dude with really long arms? Or is he something else?

He's Scottish.