This is just something that occurred to me when listening to the song. Technically everything they say is canon-compliant to Iron Legion, so there's a few hints to future events, but this story itself isn't canon to the main story. Just some fun crack because why not.

"Here we are in the future," Harley sang, throwing his arm around Peter's shoulders. "Here we are in the future and it's bright! Nothing to fear, ready to fight! I can't believe we've come so far! Happily ever after here we are!"

Peter shoved him off and scooped up Morgan, giving her a spin. "Once upon a time, I thought I'd always be in our father's shadow. Watching from the side I thought he'd always be in an endless battle. 'Til I began to hone, a power all my own, that I could feel growing stronger every day! And now we saved the world, not just that- the whole universe is saved! We did it!"

"Here we are in the future!" Harley cheered. He turned to the rest of the gathered heroes and pointed the microphone at Nebula.

She rolled her eyes, but stood up. "Once upon a time, I only lived to be a mad titan's servant. 'Til the day I got cast out, fell down to be on this planet's surface. Here I found a family, and I was sure they set me free! But in the end, I guess I never left their side. And after love and loss and all the tears that I cried, I find that-"

"Here we are in the future!" Peter, Harley, and Nebula sang together.

Humming, Harley weaved through the party and dropped into Vivian's lap. "Here we are!"

She chuckled and floated up, Harley in her arms. "Once upon a time, an android came to life with a quiet stir. Creator's deadly fate unknown until their father came in to find her. Suddenly she was crying. Beautiful, strange, disheartening. And there I was, a bundle of questions, so naive. And if you told me this I never would've believed you then but-"

"Here we are in the future!" she and Harley sang, him giving her a sad smile. She kissed his cheek before tossing him into the air. He landed next to Loki, who glared at him.

Unperturbed, he nudged him until he begrudgingly joined in. "Once upon a time, I burst to life afloat along the river Seine. A product of a war that I had no idea I had a part in. I came out lost and alone, knew nothing but a stone. But I know now exactly who I'm supposed to be, and it's a part of this family!"

The group cheered and Loki rolled his eyes, hiding back in his book.

"So, whaddya think?" Rhodey asked, setting his hand on Harley's shoulder.

The boy looked out over his family and fellow heroes. "If I could just stop right here and be finally done, finally us, finally we-"

"Wee-" Lila, Peter, Morgan, Cassie, and Vivian joined in with him, bunching up at his sides. "-eee are in the future! Here we are in the future and it's bright! Nothing to fear, ready to fight! I can't believe we've come so far!

"Happily ever after…" Lila and Cassie sang, followed by Peter and Morgan's, "Happily ever after…"

"Happily ever after," Harley and Vivian added.

"Here we are!" the group finished, laughing.