Context

This line is spoken by Dorothy, played by Judy Garland, in the film The Wizard of Oz, directed by Victor Fleming et al. (1939).

After being knocked out and swept away from her farm by a tornado, young Dorothy wakes up in a land full of really tall plastic plants and really short singing people.

Plus, the world is in color, unlike Kansas, which was in black-and-white until the mid-1960s. Dorothy looks around with her little dog, and says, "Toto, I've a feeling we're not in Kanas anymore." 

She's stating the obvious, but she's also talking to a dog, so what do you expect?

Where you've heard it

People just love to pull this one out whenever they're swept from their normal stomping grounds.

Additional Notable References

• Country singer Shanna Jackson was in a band called Not in Kansas.
• Country singer Jo Dee Messina has a song called "You're not in Kansas Anymore." 
• The first episode of the now-canceled 90210 reboot took its name from the quote.
• It's the title of a 2005 non-fiction book about magic in America (yes, non-fiction).

Pretentious Factor

If you were to drop this quote at a dinner party, would you get an in-unison "awww" or would everyone roll their eyes and never invite you back? Here it is, on a scale of 1-10.

If you're thumbing your nose at Kansas, (1) you're using this quote wrong, and (2) you're pretentious. But if you're using this quote as intended, you're just a fish out of water, and there's nothing pretentious about that.