Tim Drake, ever the detective, deduces Impulse's secret identity very quickly.
Later on in the same comic, Robin and Impulse and trying to stop a nuclear disaster. With the launch set to go off in 1.33 minutes, and Impulse having to go through trillions of combinations (the code has 5 numbers, then 3 letters, then 2 numbers), Robin is (understandably) freaking out. Impulse, however, states that "it took me a lot less than that to crack Zelda". I just love Impule's attempts to 'confuse' the computer here.
Finally, to finish it off.
The start of a great friendship, methinks.