Of course, the Hydrox cookie was invented in 1908, and bore striking resemblance to the Oreo. It was also a chocolate wafer cookie with a cream filling, created by an offshoot of the original New York Biscuit Company (Sunshine Biscuits, which today produces Cheez-Its), and also had an embossed design on top. However, Oreos took off in popularity and most consumers thought that Hydrox was actually the knockoff product. Feel guilty yet?
You can still find Hydrox cookies on the market today. They're described as being more solid and less porous than Oreos, with a tangier filling. As for Oreos (whose cream filling was actually made with lard until 1996)? Well, you know where to find them.
Adam Lapetina is a Food/Drink staff writer for Thrillist, and agrees with milk on this one. Read his musings at @adamlapetina.