Oh, it's ON. In one of the best brand-on-brand tweets ever, cinema chain AMC Theatres on Tuesday expressed its displeasure with Oreo after the Nabisco brand asked fans if they ever sneak cookies into a movie. "NOT COOL, COOKIE" admonished @AMCTheatres, which sparked an impressive 200-plus retweets. Credit for the post goes to Shane Adams, interactive marketing manager for AMC. While it's unlikely that this will spark any sort of long-term rivalry, it's still nice to see a company having some fun with another brand in the vein of Taco Bell and Old Spice. It's also a telling example of why @AMCTheatres has 136,000 Twitter followers, compared to Oreo's 53,000. Where are those 28 million Facebook fans to defend you now, Oreo? Hat tip to Deb Ng for sharing on Facebook.

UPDATE: Oreo has responded with the tweet below, prompting another tweet from AMC, below that. Someone will be crying over spilled milk before this is over.

UPDATE: Shane Adams, author of the @AMCTheatres tweets, sums up his busy day in a thoughtful blog post, with advice for other social media managers. His point? This wasn't just about being clever.