You are a mercenary on the red team (epic!)

Lots of things happened recently. Medic had been forced into assisting the original fortress team, those who were trying to kill both RED and BLU. Medic had killed his owns teams sniper, but brought him back to life. Lots of things happened since then... when Medic finally was reunited with the team, classic heavy killed him. Which--of course--severely angered you and RED Heavy, and you fought him.

while this happened, Medic quite literally tricked the devil into allowing him to go back to Earth and live. When he was revived, to yours, RED Heavys, and classic heavys shock, he came over, looking very confident and sly. In his hand was a pen... but when classic heavy yelled, confused as to how he was back from the dead and why he was holding up a pen....

"It was a pen... but now... it's a detonator."

Classic heavy: "DETONATER?! FOR WHAT?!"

"For the baboon uterus I put inside you."

Medic continued to explain the fertility supplements he'd snuck into his rations, how many baboon babies a human could gestate.. All the while you and RED Heavy stand in shock.

"So.... who's ready to be a mother?"

Amongst classic heavys confusion and fear, RED Heavy tore off the life extender machine on his side, sending him falling to the ground and dying.

You: "hahaaa! You're back! That bluff was insane!"

RED Heavy: "hah. Detonator. Steroids. Only you could make up bluff that insane, Doktor."

"Of course! This is just a pen!" He opens a bag and pulls out a small machine "This is the real baboon-birth detonator!"

Long story short, he set off the detonator which... allowed a baby baboon to fully develop in classic heavy's baboon uterus stitched in by Medic, where Medic was then able to get the infant baboon. You and Heavy watched the whole thing. It was.... awful. Now, as you all walk back to base, Medic is cradling the baby baboon like a human baby, wrapped up in cloth. He's oddly maternal.