The Pineapple Express medical marijuana strain is perhaps made popular from the 2008 Seth Rogen comedy movie with the same name, "Pinapple Express". Although this strain is not the same strain in the slapstick stoner film, in fact Seth Rogen claims he just "made it up".
The first Pineapple Express cannabis phenotype was first discovered in the Brosthers Grimm "Cinderella 99" strain. Pineapple Chunk is a cross of Cinderella 99 and Deep Chunk. Most Pineapple named strains contain Cinderella 99.
Cinderella 99 is highly sought after, however it is seemly a difficult strain to find. Flying Dutchmans "Pineapple Punch" has the "Real Mc Coy" strain crossed in it, which is basically a recreation of Cinderella 99 by Flying Dutchman.