From Bulbapedia, the community-driven Pokémon encyclopedia.
Rebecca (Japanese: マナミ Manami) is a character of the day in the Pokémon anime.
Rebecca's only appearance came in The Punchy Pokémon. She tried to convince her father, Anthony, to come home, but he told her he wouldn't until he won the P1 Grand Prix. Brock, seeing how sad she was, volunteered himself and Ash to help defeat Anthony.
Team Rocket, using a stolen Hitmonlee nearly defeated Anthony. Rebecca, not wanting her father's Hitmonchan to get hurt, jumped into the ring. Anthony jumped in front of his daughter, and then gave up. Anthony then decided to return home to his family, making Rebecca happy again.