Jerry and Kraut are more WW2 nicknames. In that they are both common male names and a famous cat and mouse combo who waged their own personal WW3, the accepted answer makes the most sense.
Fritz, however, was common in both wars. And yes, he was a cartoon cat who starred in the first cartoon rated X in the USA.
Earhart is to 100,000 other copilots to come before her. What was the name of all the other pilots who were always at the yoke beside her?