Before the destruction of Krypton, when Kal-El was a toddler, he accidentally gained limited super-powers from one of Jor-El's inventions. Flying off to explore, he came across the advance scouting party of an alien invasion. They were telepaths, and baby Kal could hear their thoughts. He did not understand their intent, but repeatedly thwarted their plans accidentally, demonstrating his super-strength, flight and super-breath. His powers wore off, but the puppy Krypto had also gained powers and saved Kal from the aliens' attempt to crush him with a log.
Deciding that the Kryptonian people were obviously far too powerful to be conquered, the aliens abandoned their invasion.
