Like The Fly, only with less Jeff Goldblum and a more dubious understanding of genetics. Thank goodness this version of the script didn't make it out of pre-production.
Redditor Sketchampm dug up this concept art from the version of Jurassic Park IV that was being kicked around back in 2007. At the time, the movie was being spearheaded by William Monahan and John Sayles.
At the time Spielberg was completely on board, calling the script the "mother of all ideas" and he wished they'd approached him sooner so it could have been the third movie instead.
Had it seen the light of day, the plot would've involved an ex-commander named Nick being tapped by John Hammond to retrieve the shaving cream can full of dinosaur DNA from the first movie. However after finding the dummy shaving cream container, Nick is kidnapped by the Grendal company (I see what you did there, scriptwriters) which is determined to cross-breed dinosaurs into an insane hybrid.
The whole insane plot summary can be found on Ain't It Cool.
Hat tip to First Showing