Cassie was born to Scott and Maggie Lang and shortly afterwards Scott was arrested for breaking into the Vistacorp CEO’s house in an attempt to return money the company had stolen to its customers. While he was in prison, Maggie divorced him and began a relationship with kind and caring SFPD cop Jim Paxton.

When Scott got out of prison, Cassie was overjoyed to see him at her birthday party, though he hadn’t been invited by Maggie or Jim. Scott gave Cassie a humorously ugly rabbit doll, which she instantly adored. Cassie was unaware that Maggie shooed Scott from the party and told him that if wanted to be a part of Cassie’s life he needed to pay child support.

Cassie knew her dad was a good man, but that he often got in trouble with the law. When he was arrested, for reasons unknown to Cassie, Scott escaped jail and it became Jim’s responsibility to track him down. Over dinner one night, Cassie told Jim that she hoped he didn’t find her dad.

Cassie discovered that Scott was Ant-Man in most shocking fashion, having her bedroom invaded by Hank Pym’s crazed protege, Darren Cross, while he was wearing a a prototype Yellowjacket suit. Darren wanted to kidnap Cassie so that he could draw out Scott for battle, but Scott arrived just in time to save her and fight Cross in her room.

Jim was able to take her to safety while Scott and Darren dueled in miniature size on Cassie’s toy train set. To ultimately save his daughter, Scott shrunk himself down so small that he went inside the Yellowjacket suit and destroyed it, killing Darren in the process. Now lost in the Quantum Realm, Scott used Cassie’s voice, which was calling out for him, to bring himself back to reality.

With her parents now copacetic and kind to each other, Cassie was able to recover from the turmoil. Though soon afterwards, Scott was arrested in violation of the Sokovia Accord after helping Captain America escape from Germany. Taking a plea deal, Scott served a two-year house arrest sentence. When Cassie would visit him, they’d have to stay inside the entire time. She still had fun however since Scott would plan very elaborate games—using mazes and role-playing missions—and dazzle her with close-up magic.

During one game, Scott and Cassie went down a slide to the outside yard and Scott’s foot broke through the front fence, causing his ankle alarm to signal the FBI. Even though Scott obviously wasn’t trying to escape, FBI Agent Jimmy Woo and his team had to search every area and aspect of the house to make sure Scott was no longer in contact with Hank Pym or Hope van Dyne.

The prize in the heist game was a silly “World’s Greatest Grandpa” trophy that Cassie had given Scott as a gift. She asked if she could take it to her school for show and tell, but Scott said she couldn’t, as he’d secretly stashed his Ant-Man suit inside of it, in miniature form. Cassie didn’t listen though and took the trophy anyway, causing Scott and Hope to infiltrate her school to retrieve it.

While Cassie was unaware that her dad was on an adventure with Hank and Hope during the final hours of his house arrest, she knew he wouldn’t break the rules if it weren’t for a good cause. So when she went to his house to find her soccer shoes and instead saw a giant ant in his place, wearing an ankle alarm, she covered for him when Jimmy and his agents stormed in. She told Jimmy that he couldn’t go upstairs to see her dad because he was very sick and barfing a lot. Jimmy went upstairs regardless, but the stalling was enough to give Scott time to switch out with the ant to make it seem like he’d been there the entire time.

Scott thanked Cassie for helping him and admitted that he couldn’t stop screwing things up, even when he wanted the best for everyone. Cassie suggested he get himself a partner to help out and he inferred that she was talking about Hope. Cassie was talking about herself though and when Scott realized this he told her she’d make a great partner.

After Scott’s house arrest was over, Cassie. Scott, and Hope all sat in a shrunken car to watch THEM! on a big screen, as if they were at a drive-in movie theater.

Surviving The Snap

Like most normal people in 2018, Cassie had no idea that Thanos landed on Wakanda and got his hands on the last Infinity Stone. However, like just about every being in the cosmos, she knew on some level that he succeeded in his mission to remove half of all life across the galaxies.

Over the next five years, Cassie survived in a radically changed San Francisco that did its best to carry on with so many important people blinked out of existence. And then, seemingly out of nowhere, she found herself reunited with her father! She assumed that he disappeared along with Hank Pym, Janet van Dyne and Hope van Dyne, but really he got stuck in the Quantum Realm, though for far less time than had passed on this side of the portal.

Lang soon took off to find the Avengers and lay out a plan to use the Quantum Realm to steal the Infinity Stone from various points in time to bring everyone back. The plan succeeded, leading to a post-battle reunion between Cassie, her father and Hope!