In the sky, you can see several floating letters that must be retrieved. You can get them by using the Lunar Landers, and they must be gotten in an order that spells LUNA. Below is a map as to where the letters are and how to get them, but for simplicity, take the lunar lander to the starting position in the building with Quick Revive and we can start from there.
Note that you CANNOT buy the landers to go to a spot, they must be called there by another player.
Here is the order:
L: Have a player standing on the lander and a teammate call them from the Stamin-Up lander, this should get an L.
U: Have a player standing on the lander and a teammate call them from the spawn lander position, this should get a U.
N: Have a player standing on the lander and a teammate call them from the Speed Cola lander, this should get an N.
A: Have a player standing on the lander and a teammate call them from the Stamin-Up lander, this should get an A.
At this point, Node 4 of the Easter Egg should be completed. Back at the metal chunk near Stamin-Up, 4 lights should appear as lit up on the metal.