Husband and wife scientists, and friends of the Flash, in the DC Universe.
Jerry and Tina McGee are scientists who both specialise in hyper-physiology, with particular interests in super-speed. This interest got out of hand, however, when Jerry started to begin applying their research to himself. He started taking some of the experimental steroids they were working on, and his mental state began to deteriorate.
Tina was aware of his developing instability, and with their boss at the research institute attempted to convince Jerry to go into therapy, but this only fed into Jerry's paranoia and pushed Jerry and Tina apart.
It was around this time that Tina received a grant from Harvard University to study the Flash's metabolism, and she met Wally West at the S.T.A.R. Lab in Utah. They were attracted to each other, and this attraction was perhaps heightened by the dangerous situation they found themselves in when the Kilg%re was released and threatened the country.
Tina decided to leave her husband for Wally, and this pushed Jerry into a jealous rage. He competed the final stages of the experiments on himself, implanting electronic devices in himself that would continuously feed steroids into his bloodstream, giving him great strength and speed equal to the Flash's (at the time, around the speed of sound). He donned a purple and yellow costume, called himself Speed Demon and attacked first Tina and the Flash and then Dr Bortz, his former boss. Unfortunately, the steroids and implants did a great deal of damage to his body, and he soon collapsed with massive internal damage.
Jerry survived only through the attention of a Russian specialist who the Flash retrieved from Siberia. After his recovery Jerry became Wally's friend, and he was eventually reunited with Tina, who had never completely lost her feelings for him even while dating Wally. Jerry and Tina now work as a team, first at the university in Central City, and currently at the Central City S.T.A.R. Lab.
Tina McGee also appeared in the (sadly short-lived) Flash TV series, as a S.T.A.R. Labs scientist who helped Barry Allen learn about his speed, made his costume and provided romantic tension.