S4 Teenage Dot
At the opening of season 4, we see this teenage version of Dot. She is so busy managing the construction of her new diner that she had forgotten to attend her father's presentation on the gateway machine. When she had remembered, it was already too late, the gateway machine blew up deleting the sprites in that area.
Dot helped Welman prepare for the presentation by giving him sample questions to answer, and giving suggestions to him on how to make it a more understandable presentation. She had promised Welman to be there on the big day. However, the contruction of her diner took precedence. As a result, she can't help but feel guilty for not being there with him.
Because of her selfishness, she has changed (both physically and mentally) and has become a more responsible sprite.