Dizzy and Daffy Dean's shoes made sure everyone knew which brother was which

Dizzy and Daffy Dean were not twins. Dizzy was two years older and began his career four years before his brother. They didn't even look that similar -- the eldest Dean with a slightly rounder face than his brother, Daffy with a more prominent chin. It wouldn't be impossible to keep the two straight, in other words.
Still, when Daffy joined the Cardinals ahead of the 1934 season, Jay and Paul wanted to make sure everyone could tell them apart. So, as if they were giant Toy Story fans six decades early, they identified themselves on the bottoms of their shoes for this photo.
Things worked out for the brothers in '34, too: They combined for 49 wins, the Cardinals were World Series champions and Dizzy won National League MVP. After that, they probably didn't need their shoes to distinguish themselves. 
And it was even easier a few years later, after Dizzy was traded to the Cubs and the two shipped off to different Spring Training locales. 

Although, who knows? Maybe their shoes still said "I'm Dizzy" and "I'm Daffy."