Hoopy the Hoop

In Portal, Hoopy the Hoop was a hoop fallen from the sky among the wreckage of GLaDOS at the end of the game.

As stated in an interview, "Opening The Portal: Exploring The Game's Development", with Valve, they never expected "The Cake is a Lie" to become such a huge hit. They expected, if anything, that Hoopy the Hoop would become the meme derived from Portal. Erik Wolpaw explains, "We thought we should have a warehouse full of Hoopy t-shirts and mugs and posters…we would watch that hoop roll by over and over again. That was the part of the game we were most proud of, and nobody cared."

Portal
Hoopy the Hoop rolls across the screen at the end of the game

Portal 2
Hoopy is known to appear in a few places within Portal 2. His earliest known appearance is in Her Chamber, where he lays slightly to the left of what could be described as GLaDOS' head; his second known appearance is underneath a floor panel in Test Chamber 2. He makes his third known appearance behind a desk in Test Chamber 6; this is the same den as referred to by the Final Transmission achievement.