Gaby

Gaby was the biological mother of Herbert Powell, who gave birth to him after having a one night stand with Abe Simpson while he was still with Mona.

History
When Abe Simpson visited the local carnival at Shelbyville (before marrying Mona), he was drawn to Gaby at first sight. She had sex with him for money. A year later, when the carnival returned to Shelbyville, Abe discovered that she had given birth to their son.

Unmarried and ashamed, Abe and Gaby took their infant son to the Shelbyville Orphanage. What happened to her after this is a mystery. Their son was later adopted by the Powell family and renamed Herbert Powell, who went on to be the founder of Powell Motors in Detroit, Michigan.