There are 25 hidden competitive minigames in It Takes Two, five of them in The Attic. They will all be marked with a hovering tambourine, and finding all 25 will get you the Minigame Megalomania achievement or trophy. You can then access all of these minigames at any time from the menu — the following is in order of how the games are listed in the menu, slightly different from the order in which you find the games.
While four minigames are marked as being a part of the Setting the Stage segment, this is a little misleading. They are all in the starting area, but more sections of this area will open up as you complete more gameplay segments.
After completing Setting the Stage, platform above the Slotcars minigame to find a mysterious big red button and a light blue radio. In front of it is a chair, and you two can complete in quick rounds of Musical Chairs. The button prompt for sitting on the chair changes each time, so pay attention.
After completing the heavenly Symphony section, you will go under a vent — before doing so, notice two arcade machines on the right corner. You’ll enter the world of the arcade game, running forward to the finish line while avoiding glowing purple obstacles.
The first minigame you’ll find in Setting the Stage is fairly easy to encounter — it’s just on your way to the first proper puzzles of the segment. Control the cars’ speed with the right trigger, but slow down on turns, otherwise your car will fly off.
When you return to the attic after Setting the Stage, turn to the right to find a chessboard. You can play a quick game of traditional chess, though you will have to physically walk to each piece to select it. If you don’t finish the game through checkmate, someone running out of time will do so instead.
In the Symphony chapter, look for a low cloud in front of the pit and organ after you free the entire orchestra. You can play a game of Volleyball here, jumping to bounce the ball across the net or dashing to “Smash” the ball — just be sure to not accidentally dodge roll by accident and totally miss the ball.