A before B, except after W.

Dad:  “Tom, can you put these DVDs away in alphabetical order?”
Tom:  “I've got Fantastic Four, where is the "W"?”
Dad:  “There is no "W" in Fantastic Four.”
Tom:  “I know, but this one goes right after "W" because in the alphabet it goes W F Y Z.”
Dad:  “It's "X". Not "F".