Assuming the higher the resistance, the slower the Bop-It, place the pot in series with the original resistor and use the switch to short around the pot.

Hasbro Bop-It Micro Series Repair - iFixit Hasbro Bop-It Micro Series Repair - iFixit

Carefully seperate the two parts containing the speaker and the batteries. NOTE: The big buttons will pop of and the two springs on each button will too. Catch everything before you loose it. Remove the 4 screws on the bottom. NOTE: One of the screws is longer than the rest. Make note of it. This is the most scary bit: Take the game apart. You do not need to remove the batteries to do this. WARNING: You might break the game if you try this mod. Only do this if you are quite sure that you are capable of handling springs and wires jumping all over the place. If you doubt your own technical prowess, then you might be better off not screwing around. Stuff will shoot off in every direction if you're not careful, and even then. Pay attention and work slowly. Build the circuit as indicated by the schematic diagram, using wires and solder. Re-use the resistor that was previously removed from the circuit bord.The Bop-It Micro Series handheld gaming device was released by Hasbro in 2014. The game features single and multiplayer modes. It is a smaller version of the full version, Bop-It. The Bop-It Micro features twist and pull levers, as well as a the Bop-It center button.