The new universe cooled and the energy Greg released from Ragnaros gradually acclimated.
But it was all in Greg's head.
In reality Manny had just called Greg a Ploopy in front of the whole school and he needed to do something fast.
Greg knew his mother was having an affair with the Greek god Poseidon, after all he literally had the body of a Greek God.
This affair had been going on for at least 5 years, so there was a 1/3 chance * 1/6 chance or 4.6 percent chance that he was a demigod, or son of Poseidon.
But 5% was enough to save his dignity.
Activating a lesser known ability of Poseidon, he used hydrokinesis to create a tsunami and wash everyone out of the auditorium.