High Speed Hijinks is the fifth and final Challenge Act in Sky Sanctuary Act 2 in the console/PC version of Sonic Generations. It is unlocked after clearing every Stage in the classic era and is playable only as Modern Sonic.
The player takes control of Modern Sonic in Sky Sanctuary Act 2 with no supporting characters. As the name would imply, during this Challenge Act, everything, excluding Sonic himself, move at double their normal speed. The increase in speed is meant to make it harder for the player to navigate through the given area to the goal. This includes enemies such as the Eggrobos and the lasers they shoot, as well as moving platforms.