Yatter! Yoshiko Ohta was one of the earliest cast members of the series and voiced it’s first two male heroes, Time Bokan’s Tanpei and Yatterman’s Gan-chan.
While she didn’t do terribly much voicework in anime, the ones she did had a big impact on the media in general. Such characters are Leo / Kimba in the first adaptation of Jungle Emperor Leo / Kimba the White Lion, the title character of Himitsu no Akko-chan, Princess Sapphire from the titular Princess Knight and the original voice of Nobita Nobi from Doraemon.
Amusingly, those last two characters were later voiced by Noriko Ohara as Nobita (from 1975 up to 2005) and Mari Okamoto as Sapphire (in one episode of the 80s Astro Boy). In other words, Doronjo and Ai-chan replaced Gan-chan in those roles.
After Time Bokan Royal Revival, Yoshiko Ohta retired from doing voicework. She did come back to voice Tanpei and Gan-chan again for the PS1 Banpresto games, but by 2008 wasn’t up for it anymore, hence why Gan-chan has a different voice actor.