Reader Colton S noticed a brief Rush 2112 reference in a recent episode of Cartoon Network's Adventure Time (Season 5, Episode 49 - Bad Timing - aired 3/4/2014). Towards the beginning of the episode Princess Bubblegum unveils her new orb-shaped time travel machine, and explains how it works and how it is controlled by a pair of special gloves. The green pair of gloves display the time and, for one split second as she is adjusting the time, it reads 21:12. You can watch the episode online here and the reference occurs at about the 50-second mark, but if you blink you'll miss it so here's a screenshot.