Lupe's Thumbappears in The Marble Champ

In The Marble Champ, Lupe decides that she wants to be recognized for sports. She is determined to win at the neighborhood marble competition. While she trains, she spends a lot of time doing arm, hand, and especially thumb exercises. A naturally skinny girl, her thumb rapidly develops into a powerful appendage ideal for shooting marbles. After a few weeks, Lupe's mom notices her bulging thumb muscles while they are washing dishes. Lupe's thumb is a symbol of her determination to succeed.