Well another flaw in the 'X-MAS' episode... when leela and fry are skiing, they are heading for some Pine Tree's and leela says 'Trees down', and that happens, bla bla... but then when they are looking for a xmas tree, H. Farnsworth says that the pine trees has been extinct? WEIRD... that's like a flaw in 2 minutes animation..

they were probably fake, i mean, when did you last see a pinetree that could fold itself into the ground on command?

Ya, the trees most likely were fake.  Even if they weren't, those trees could have been spruce, tamarack, or any other type of evergreens, not neccesarily pine.  But they had to have been fake.

Yeah, really!!! Even I have a fake plastic pine tree!

but why the hell would they have fake trees outside??? (i mean ´when you saw them through the window) It makes no sence. The folding trees could be fake, but what about the others????????

Actually I think the point of it was to be funny. I mean were you expecting a palm tree. It's also funny because they could have the fake ones quite easily.