Tina Pinciotti

From Groovypedia, the "That '70s Show" Wiki

Tina Pinciotti, as portrayed in her only appearance in the show, was the younger sister of Donna Pinciotti. Her only appearance was in the episode Eric's Burger Job, although there was mention of her in a later episode, Vanstock.

Tina was a redhead like her sister, and she was three years younger. At the time of her only appearance, she was said to be 14. Her sister, Donna, was 17 at the time.

The only other time she was mentioned was in the season 2 episode, Vanstock, where, in the closing credits, the question was asked as to what had happened to her.

In later episodes it was alluded to that Donna was an only child, effectively writing Tina out of the show.