Reading Digital Signal Inputs Without Altering Voltage, Current, Timing, etc

Getting my feet wet on my first Arduino project, and I ran into a bit of a snag.

I want to take the data line of Gamecube Controller (pin 2 in Nintendo Gamecube Controller Pinout) and analyze it with my Arduino Micro without affecting the signal being sent along it between the console and controller. The ultimate purpose would be to be able to have the controller connected to the console while recording it's input on a PC. My particular issue is one resulting mostly from ignorance.

Can I simply splice a wire onto the 3.43V Data line of the controller, run it to one of the Digital Input pins on the Arduino, and not cause a distortion in the voltage/timing that the console is reading down the line? And if not, what kind of circuit design would most easily achieve this?

While it is a fundamental law of physics that you can't take a measurement without affecting the system you measure;

Can I simply splice a wire onto the 3.43V Data line of the controller, run it to one of the Digital Input pins on the Arduino,

Should work.

You should just be able to tap into the line and run it off in parallel. You basically want a relatively high impedance input in your measurement device to not interfere much with the normal operation, like with an Oscilloscope or DMM in voltage mode. If you can figure out the impedance of the game-cube input,it would help, but that could be complicated in itself (It probably is not just the DC resistance, though that is a good place to start).

If you can figure out the impedance of the game-cube input,it would help,

I doubt it, all inputs on digital systems are high impedance and outputs low impedance that is how digital systems work.

Logic has what is know as a fan out, that is how many inputs an output can drive. This is typically about 20 so adding another input is not going to matter much.

though that is a good place to start)

No it is not.