Zee Egg is Mario's last available Bros. Attack in Mario & Luigi: Dream Team. Unlike his other Bros. Attacks, Mario obtains this by speaking to Eldream in Mushrise Park once all 52 Pi'illos scattered across Pi'illo Island are rescued, doing so yielding the 10 Attack Pieces for this attack. The attack costs 15 BP and hits all enemies on screen at once. Mario and Luigi's influence this attack's power.
Upon use, Mario takes out the Zee Egg and throws it into the arena, summoning the Zeekeeper. The Zeekeeper carries Mario and Luigi up into the sky and shoots out a Wake Orb, which descends toward the enemies, the Zeekeeper chasing after it. The player must use the to move the Zeekeeper from side to side to line him up with the Wake Orb, and press either or when Mario or Luigi jump towards the orb to make them pound it with their hammers and increase the power of the attack, after nine successful hit with the bros., the final hit will always be Mario and Luigi go to hit the orb at the same time and need to press and at the same time. If Mario and Luigi hit the tenth hit, the attack will yield an "Excellent!" rating and the Wake Orb will explode on the target, heavily damaging it and slightly harming the other enemies.
If Mario and Luigi don't hit the Wake Orb enough times, the attack will go on as normal, but deals less damage with either an "OK", "Good" or "Great" rating depending on how much it was hit beforehand. Finally, if the player fails to press the button to make Mario or Luigi properly hit the Wake Orb, they'll fall past it and will begin falling at a slower pace than the Zeekeeper. They can then either be caught by the Zeekeeper which continues the attack or fall off screen, the latter ending the attack prematurely.