A teriyaki-style dipping sauce created as a tie-in for Disney's "Mulan," available for roughly three months alongside McNugget Happy Meals in 1998, then gone. It sat forgotten for 19 years until the animated series "Rick and Morty" made the sauce its protagonist's entire motivation for existing.
A Change.org petition to bring it back gathered 38,000 signatures before the "Rick and Morty" season even ended. McDonald's brought it back for one day in October 2017, severely underestimated demand, and watched crowds at understocked locations descend into chaos.
When there wasn't enough sauce to meet the extreme demand, some protested, police cars lined up outside restaurants, and McDonald's ultimately apologized and shipped out 20 million packets in a second return in February 2018. A surviving 1998 packet sold on eBay for $14,700. The sauce itself, by most accounts, tasted fine.