Curt Connors is a scientist who becomes the villainous "Lizard." In the Sam Rami trilogy, he was played by Dylan Baker in a very small role as Parker's teacher. In the Marc Webb film, Connors is now played by Rhys Ifans and presented as the main villain of the film.
Doctor Curtis Connors aka the Lizard was one of the very first Spider-man villains created. Designed by Stan Lee and Steve Ditko (who had also created Spider-man), he first appeared in Amazing Spider-man #6 in 1963, less than a year of the creation of Spider-man.
Lizard's origin story is similar to that of Robert Louis Stevenson's DOCTOR JEKYLL AND MISTER HYDE: Doctor Connors was a respected and noble scientist who (in an experiment trying to regrow the hand he lost valiantly serving his nation in the US Army) accidentally released his inner dark side. Connors has appeared as a primary villain of Spider-man in most of his comic book series, but has also appeared in human form as a valuable friend and ally who develops formulas that Spider-man uses to combat villains such as Rhino, Iguanodon, Kingpin, and Freak. He has always been a quite tragic character who desperately wants to do good but is always consumed by his insanity; in mainstream continuity he eventually loses control and kills his son.
Connor's first big screen appearance was in SPIDER-MAN 2 where he appears as a teacher and close friend to Peter Parker. The character was also in SPIDER-MAN 3 where he explains to Peter the traits of the Venom symbiote and is left with a sample. This likely would have led to his transformation in a later film, but conflicts between Sony and Sam Raimi causes the franchise to be rebooted with a new creative team.
Lizard is the primary antagonist in the 2012 Spider-man film THE AMAZING SPIDER-MAN.