"Perhaps the strangest episode - and one that rates as a Golden Age classic in creative fantasy - occurred when Scarlet discovered her invisible power was contagious. It began with a casual stroll down the street during an invisible state when a youth, coming the opposite direction, bumped into her and knocked himself silly. Thrown to the ground, the dumbfounded lad scratched his head and tried to figure out what had happened. As a gesture of apology, Scarlet kissed the boy on the cheek. Result: the boy became invisible!"
Here's that very strip from March 5, 1944.