Thunderstorm required. Scarab & Envy recommended
To get this Easter Egg to unlock you must complete the entire mission using the settings above without being hit by a single enemy bullet! Luckily you can use the Scarab Gun and the invisibility provided by the Envy skull during your playthrough. If at any point you are hit with an enemy bullet, your screen will blink red and your shield will take damage. You MUST "Last Last Checkpoint" (or die) and try again.
If you make it through the entire level into the bomb room without being hit by a single bullet, a special dialogue will come over the intercom; "Paging Megg..." and the achievement will unlock.