Mikey went back to the sewers, where he met up with his brothers. Don finished the time machine once Mike showed up.
"Guys, there's something I need to tell you," Mike said, taking a deep breath, "It's about the bump on my neck."
"You're growing a second head," Leo responded.
"You already knew? How?"
"It has a mouth and two eyes already."
"Wha….?" he looked at the second head. Surely enough, there were two sets of eyelids squeezed shut with the actual eyeballs developing inside. "What should I do?"
"...You know what you have to do," Leo responded.
"...Um….."
"Look, Mikey…so maybe you're far from the most serious guy in the world, but we trust you to make sound judgements when it comes to, um, these kinds of things."
The other three turtles hugged Mike, telling him that they believed he could decide for himself what to do.
Mikey's eyes started to water as he said, "Thanks, guys…I love you."
"We love you to," Donatello smiled as he turned on the time machine. There was another group hug as it turned on.
"...How did this even happen?" Mikey asked, "I-it was completely unexpected…."
"No one ever expects it," Leo told him, "It just happens one day."
Then, the head grew into a full head, popped off, and flew away.
"Good bye, second head!" Mikey shouted, waving and crying with tears of joy. They grow up so fast.