I don't think you can get the Banana Kush that's used in these crosses expect as a clone. Here's the story on the Banana Kush that Crockett is using
Breeder: Crockett
Hybrid: OG Kush x Skunk Haze
Info: This is a variety that we created about 10 years ago that i began to call "Banana" because it has a faint banana smell, but because i had mistakenly taken a name that had already been used, we renamed it "Private Reserve". But locally we still call it Banana. [...] I'd been searching for a long time for a particular OG Kush cut, and when I found it, I grew it for a while. It's called the Ghost OG. [...] I like the Ghost cut because of the Nug size and the yield. It's not a huge yield, but for an OG it's good. I mixed it with a local Skunk variety we've been growing around here for years, which is actually an ancestor of the Haze that everybody in Amsterdam is crazy over. It's a mix between those two, and the genetics that came of it were just incredible. It's just a freak of nature. [...] I thought they would cross well because they are just such different spectrums. The OG is so indica and the Skunk Haze is so sativa. The Kush cut was probably 8 or 9 years old when i got it and the seeds from the Skunk Haze are back from the early seventies. I wanted to mix that Skunk Haze with something because I knew it was something that no one else had. It's really unique. And now i have something noone else has
http://en.seedfinder.eu/strain-info/Banana_Kush/Unknown_or_Legendary/