A S.H.I.E.L.D. agent thanks Iron Man for coming at such short notice as he arrives at bunker. The agent explains that since S.H.I.E.L.D. took stewardship of Bruce Banner and his alter ego, the Hulk, they have been developing fail-safes in case he ever gets out of hand. Before he’s able to tell Tony about their latest project, he comments on how cool Tony’s armor is. Tony asks if everyone on the project is this easy to impress and is surprised when the agent tells him no. Tony opens the door to the bunker to find Beast working on a tablet, with a Hulk-buster robot behind him.
Tony comments on Beast’s new appearance, asking him if he drank one of his experiments again and calls him out for creating a rip-off of his Hulk-buster armor. Beast says that the Hulk-buster project is a S.H.I.E.L.D. project, while the fail-safe he himself created is a serum that grants agents Hulk-like strengths for short periods of time. Beast admits that there were complications with his creation. Both the agent who tested the serum and Beast agree that they don’t talk about the incident, much to Tony’s disappointment.
Beast also admits that he’s can’t help S.H.I.E.L.D. with their current problem, a virus that has infected the Hulk-buster robot with a hostile code. Tony immediately gets to work, confidently telling Beast that he’ll let him know when the fix is something he can power-chug. Tony disables the fail-safes so he get further into the code. The system corruption rises at an alarming rate until it reaches 100% and the machine powers on. Tony admits to Beast that he just got his ass kicked.
Beast questions Tony’s tactics and asks him if he’s drunk. “Much worse than that,” Tony says as he armors up. “Someone out there is better than me.” Iron Man blasts at the robot with a powerful repulser beam that exhausts his power reserves. The robot easily deflects it and grabs Iron Man by the arms. Beast climbs on the robot’s back while the robot rips open Tony’s helmet at the seams.
Suddenly, the Hulk smashes through the roof, knocking out the robot in a single hit! The Hulk looks around, still out of control. The agent from earlier rushes over to him and shows him soothing psychic imagery, such as puppies, to calm him down. Hulk reverts to Bruce Banner and asks what happened. Beast tells him that he disproved a S.H.I.E.L.D. project’s function and saved their lives. Iron Man asks to take another crack at solving the problem.
Looking at the robot’s damage, Bruce tells them they’ll have to find another way to heal their bruised egos. Bruce thanks them and says it’s good to know that the world’s top minds are keeping an eye on him. Beast and Iron Man walk away and Bruce approaches the robot and pulls out a USB drive with “For Hank & Tony” written on it. He tells the S.H.I.E.L.D. agent that it was a reminder for everyone that Banner is the smartest one there is.
Thor falls from the sky crashing multiple times on a field of endless snow. Iceman lightly asks him if he’s alright and offers to pick up the hammer he dropped but jokes about not being worthy enough. He asks Thor if a nun or Ryan Gosling ever attempted to lift it. Thor is not amused as the two stand before an army of Frost Giants.
Iceman claims to have met them before but Thor tells him that this is Ymir himself, leading a new Jotun invasion of Midgard. Iceman asks Thor what he plans on doing, suggesting that a direct attack may not be the best idea but Thor doesn’t listen and flies headfirst into the army. Thor is quickly grabbed and thrown again, prompting Iceman to ask him if he has a “Plan B.”
Ymir taunts Thor, telling him that his lightning is nothing and there is nothing he can do to stop the invasion of Midgard. Iceman constructs a hammer of his own and jokes about Thor’s hammer being nice. “You think jokes will win this day?” Thor asks. “I haven’t tried them all yet,” Iceman replies.
Thor compares Iceman to Hawkeye but says that after he makes jokes, Hawkeye actually does something. He tells Iceman to summon the rest of the X-Men or Avengers while he deals with the situation with thunder and lightning. Iceman tells Thor that he should wait, because he believes Ymir is playing with him. Thor refuses to listen and strikes at Ymir with strong strike of lightning.
“Fool!” Ymir cries out. “Now it begins.” The leader of the Frost Giants reveals that he is holding the Casket of Future Winters and it seems that Thor’s lightning just powered it up. Realizing his mistake, Thor tells Iceman that The Casket of Ancient Winters was an artifact created by Ymir that contained the sum of all cold. Thor managed to send the casket outside of Ymir’s reach but Ymir has created another one. Ymir calls upon the casket and the icy winds of oblivion. He holds the casket to the sky and unleashes cold itself.
Iceman jokes that now at least now every Christmas will be a White Christmas. Thor has had enough and calls Iceman a fool for continuing to joke when Ymir could very well end the world. Iceman admits that he jokes to keep the X-Men and Avengers from going insane due to all the grim they face. Iceman tells Thor that he’s right about him not taking the situation seriously and asks Thor if he knows why. “Nay,” says Thor curiously. “Because these idiots just turned the world into ice,” Iceman says as he rises into the sky. “And I’m Iceman.”
Suddenly multiple giant versions of Iceman rise from the Earth, towering over the Frost Giants. They quickly overpower the Frost giants in battle as Iceman and Thor go after Ymir. Iceman tells Ymir that unleashing the cold of the casket has made him more powerful. Iceman grabs the casket as Thor finishes Ymir off with a heaving lightning strike, sending him way, back to Jotunheim, to “lick his wounds.” Before Iceman can finish a joke about Ymir’s tongue getting stuck to himself, he collapses along with his giant replicas.
Thor grabs him. Iceman admits that he used too much power, trying to look good in front of a god. Thor laughs loudly, appreciating Iceman’s joke about Ymir’s tongue freezing to his wounds. “I don’t think you’re taking this seriously…” Iceman says as Thor flies him off to safety.
Sinking below is the Casket of Future Winters, which Iceman dropped when he collapsed…