Hey ShamahVisuals, thanks for pointing this out.
I had not actually tested the Windows version with an OUYA controller, but from what I can tell from briefly testing now, the 'O' button is used for accepting on the menus, like the Main Menu or the Pause menu in game (which is mapped to the 'U' button on the OUYA controller when playing on Windows).
Actually, other than testing what all of the buttons do, there is no need to press the 'O' button while playing in Game.
Seems like in-game, the OUYA 'O' button on Windows is both select (for menus) and pause (but without the actual pause menu) at the same time. This is why using a controller mapping asset like Rewired or InControl would help for gotchas like these, but due to time constraints, I had to use the default Unity mappings which are one thing using an OUYA Controller on an actual OUYA and something else entirely when using an OUYA controller on a Windows PC.
Again thanks for finding this bug, have you tried with an Xbox 360 controller or with keyboard controls?