Herb Overkill is a scientist and inventor who is also a super villain.  He is married to Scarlet Overkill, a celebrity super villain who is widely considered the greatest one the late 1960s has to offer.  Herb supports his villainous wife by inventing weapons, devices and other gadgets for her to make use of during her crime sprees.  And he is every bit as inventive, intelligent and devious as Dr. Nefario and Vector.

Herb has also thoroughly embraced the English mod subculture (even though he is an American).  Everything about him, from his hair style, his fashion sense, his demeanor and body posture, to his use of slang and his general behavior is absolutely indicative of how much he loves being a mod. 

Herb is far more easy-going, laid back and affable than Scarlet, and is more of a swinger as well.  While he lives under his wife's shadow, he doesn't let it bother him.  Rather, he revels in their romantic relationship and the deviousness of their many schemes and adventures, all while fully embracing 1960s British culture.  (Of course, because of his more easy-going, laid back and affable nature, he's also more easily distracted from his schemes, and can become dejected and depressed when he is thwarted.)