I happened to be driving down the road recently when a bright red sports car went by bearing the vanity license plate 4 MY EGO. Then and there came a dazzling revelation: the whole subject of vanity license plates as a vehicle for wordplay has recieved very little attention from logologists.
Eckler, Faith W.
"Vanity of Vanities,"
Word Ways: Vol. 19
, Article 2.
Available at: http://digitalcommons.butler.edu/wordways/vol19/iss4/2