So well hidden was this little easter egg, that not even Tim Schafer was aware of its presence.
Since the reveal, fans have been trying to find Crowley's date of birth, but it was proving very tricky, and even reaching out to him over social media had been fruitless. Enter ScummVM developer Digitall who examined Full Throttle's game code and discovered Crowley's date of birth hidden deep within:
14 December, 1962.
That's right, entering 12-14-62 into Malcolm Corley's safe will reveal a little secret that nobody, not even Tim Schafer, was aware of.
The easter egg itself is very silly, and isn't the secret to Monkey Island or anything, but it is amazing that we're still finding secrets after all these years! Enjoy!
Source: Double Fine