Within the game is a series of hidden developer messages. The first one, which reads "PRESS CTRL-Z DURING THE CARTOONS," is accessible by enabling joystick mode and pressing button 1 after navigating the joystick cursor to the bottom-left of the title screen. If the player complies with the message and presses Ctrl-Z during the game's cutscenes, they'll be given different fragments of a cipher message; piecing them together and decoding them reveals the sentence "ENTER THREE LETTER CODE WHEN YOU RETIRE." Likewise, pressing Ctrl-Z while the game displays the cipher fragments brings up the phrase "DOUBLE HELIX," alluding to the shape of a DNA molecule. Accordingly, if the player types "DNA" on the retirement screen that appears after beating the game, they will receive a congratulatory message from programmer Robert Cook.

The complicated nature of this Easter egg resulted in it going undiscovered until 2016, when game preservationist 4a.m. tried cracking the ROM's atypically complex antipiracy protections while attempting to preserve as many Apple II games online as possible. Cook sent 4a.m. a congratulatory message on Twitter after discovering the secret, jokingly stating that "I assumed it would take a thousand, but you solved it in a mere 33 years."