In the early 1900s the Moonbeam Sundae was a standard soda fountain menu item. I haven't been able to determine where it originated, but identical recipes appear in volume 20 of The Spatula (a trade magazine for pharmacists) in 1913 and in volume 4 of National Drug Clerk (same) in 1916.
"Put a slice of fruit cake on a small plate. On this put a No. 10 mound of vanilla ice cream. Make a semi-circle of cream at one side of the mound to represent the moon. Over the ice cream pour a ladle of crushed orange. Serve a couple of wafers on the dish."
These days the Moonbeam Sundae seems to have been completely forgotten, being vaguely, barely relevant to today's children only in that it appears as a special treat in Edward Eager's classic novel Half Magic (pub. 1954). However, Eager saw no reason to describe the recipe of the standard moonbeam sundae, and instead described what made the one in the book so special -- it was served with three kinds of sherbet and lots of pineapple syrup -- and thus misleading generations of children.