Some players -- like the now-immortal Keith Comstock -- pose for them on purpose. Some are semi-tragic mistakes. Others, well, we just don't know.
What we do know: From bat-handle obscenities to boa constrictors and mascot photo bombs, these are 10 of the funniest and most memorable baseball cards ever.
Billy Ripken 1989 Fleer
With perhaps the most famous error card ever produced, Billy Ripken is known to this day as much for the bat handle pictured in his 1989 Fleer card as he is for his career with the Baltimore Orioles or his famous sibling.