'The Man From U.N.C.L.E.'
"The Mad, Mad Tea Party Affair"
"The Girls Of Nazarone Affair"
Dr. Egret was the closest thing 'The Man From U.N.C.L.E.' would have to a recurring villain like Wo Fat or Dr. Loveless or Wil Wheaton. She was an evil scientist working for THRUSH, but by the end of the first episode we learned that she had been in disguise the whole time. (She pulled off her latex face a la the IMF agents.)
And "Dr. Egret" was probably an alias as well. When next we saw her, she was a blonde going by the name of Madame Alceste Streigau.
But those two episodes were her only appearances within the show. The producers never saw fit to bring her back.
However, she may have shown up in other TV series....
All we need are evil scientists (Madness not a deal-breaker) who are women and who survive the end of the episode in which they appear. And they should follow the Toobworld timeline - you don't want to get carried away and claim that Dr. Faustina from 'The Wild, Wild West' was the same woman as Dr. Egret. But claiming her look-a-like descendant Dr. Cassandra Spellcraft from 'Batman' would work...
So howzabout it? Can you think of any female mad/evil scientists who might have been Dr. Egret? I don't think we even have to take into account aging as the years passed because she was such a master of disguise.
But I'm not sure her lifespan should be extended too much farther into the new millennium....