"Milk's favorite cookie" was literally drowning in the stuff when Post's Oreo O's cereal hit stores in 1998. Post kept things fresh by giving the O's flavor upgrades over time. In 2001 Oreo's signature cream filling was coated onto the O's to make them taste even more like the cookies. A year later, "Extreme Creme" Oreo O's introduced marshmallows — and people were all about it. This is why Oreo O's sudden discontinuance in 2007 was a shocking disappointment to its legions of devotees. Sadly, Oreo O's got lost in the fold when Post and Kraft parted ways that year. Fans the world over regarded Oreo O's as a fond and distant memory — well, except for one part of the world that never stopped selling it: South Korea. This breakfast cereal did make a comeback to cereal aisles in the summer of 2017 and is still going strong — in 2019 they even brought back those freeze-dried marshmallows. Yes, I realize the title of this series is those that disappeared and this cereal has comeback, but it was gone for 10 years so I decided to include it, an author's prerogative. Have you ever tried this cereal?

Kellogg's had a wild notion back in 1997 when they launched Wild! Watermelon Pop-Tarts. They even added an exclamation point after "wild" to remind you how daring it was to marry watermelon and toaster pastry as one. The flavor marriage proved to be short-lived. Wild! Watermelon Pop-Tarts were branded as a limited edition offering, but the exclusivity didn't do much to boost sales. As the '90s drew to a close, so did Wild! Watermelon's ill-fit presence in Pop-Tart's rotating flavor selection. But it wasn't Kellogg's last attempt to present us with the idea that heated watermelon jam paste could be appetizing.  In 2015, the neon pink and green frosting returned with the release of Frosted Watermelon Pop-Tarts. Once again, the flavor was unpopular with consumers, who noted that watermelon Pop-Tarts tasted less like breakfast food and more like sweet and sour candy. Yet Kellogg's refuses to believe that Pop-Tarts and hard candy aren't compatible and resurrected the watermelon Pop-Tart for a third time in 2017 through a limited collaboration with Jolly Rancher. Before long, Jolly Rancher Pop-Tarts also disappeared from stores. Would you like this Pop Tart?

Carnation Breakfast Bars were the solid alternative to the brand's bestselling meal replacement drink mix, Instant Breakfast. The '70s-era advertisements (and the front of the wrapper) suggested that drinking a glass of milk alongside a Carnation Breakfast Bar made it a complete meal, teeming with protein, vitamins, and minerals and supplying the human body with energy — so that's what many people did. The bars were chocolate covered and came in flavors like chocolate chip, chocolate crunch, granola with raisins, granola cinnamon, and granola with peanut butter. By the 1990s however, Carnation Breakfast Bars' sales were declining. A 1994 rebranding by Nestlé (which acquired Carnation in 1984) played up the 19 vitamins and minerals contained in every bar, sold a non-chocolate-covered version, and even included an informational phone line at the bottom of the ads that skeptics could call to make statements or ask questions. The efforts weren't enough. Carnation Breakfast Bars vanished in 1997. In the mid-2010s Nestlé sold a similar product, the Carnation Breakfast Essentials Nutrition Bar — but it failed to fill the void left by the original Carnation Breakfast Bar and was eventually discontinued. Have you ever eaten a breakfast bar?