The mighty elephant, biggest land animal on Earth, is reduced to a quivering panic by a tiny mouse. It is a cartoon staple and a pub fact: the giant with one absurd weakness, scuttling away from a rodent.
There is no solid evidence elephants have any special fear of mice. The idea goes back at least to ancient writers and got cemented by cartoons, but when people have actually tested it, elephants mostly ignore mice or react only the way they react to anything small that darts unexpectedly near their feet. Elephants have poor eyesight, so a quick movement at ground level can startle them, exactly as a sudden movement might startle you, but that is a reaction to surprise, not a phobia of mice specifically; they would react the same to a rolling ball or a scurrying anything. Mythbusters even filmed wild elephants and saw curiosity and caution rather than terror. So the great elephant-versus-mouse showdown is mostly cartoon physics. A startled elephant is reacting to a sudden small thing moving, not nursing a lifelong dread of Jerry.