"The Puzzle of Wild World!"
Superman returns from a mission in deep space, to find the planet Earth transformed into a bizarre parody of itself. While trying to reason out what has happened and possibly set it right, Superman runs into Professor Farlow Nurd, the man who is responsible for the Earth's current strange predicament.
"Tales of The Legion of Super-Heroes, Sun Boy's Lost Powers!" reprinted from Adventure Comics (1938) #302.