- Katie and Aaron's sibling relationship in general. Katie's very first comment about her little brother is that he "gets" her, and the two of them are shown to be very close, always horsing around with each other, sharing a Secret Handshake, supporting each other's interests, and trying to cheer the other up when they're feeling down. Heck, Aaron's reason for going along with their dad's road trip plan was that he was sad about Katie going off to college and just wanted to spend more time with her. Given that both are implied to have difficulty making friends, it's extra sweet that they've at least had each other.
- Katie appearing excited when she learns Aaron has a crush on Abbey Posey. Even when Aaron desperately tries to deny it, she encourages him by telling him he shouldn't have to hide his feelings. (Kudos to how Katie is shown to be very open and casual about her own homosexuality.)
- The Mitchells adopt Eric and Deborahbot as part of the family.
- They even consider Linda as their adoptive mother after she saves them from the Giant Furby, saving them in turn.
- Meta: The photos of the cast and crew with their families in the credits. Both past and present.
- One of the home videos seen early in the film, where Rick comforts a young Katie who's afraid of leaving for camp by giving her a wooden moose figure. Especially once we learn that's the one thing he has left from the log cabin of his dreams that he built when he was younger. Even baby Katie acknowledges that that's "his favorite thing" that he's giving her just for her comfort.Rick: You know how to say "I love you" in moose language?"
- Comes back in the epilogue, too, when Katie finally gets dropped off at college.
- The home video where Rick and Linda move out of Rick's log cabin, which was his lifelong dream to build all by himself, all for the sake of baby Katie. We've been told how this event kind of made him drop expressing himself creatively, so we expect it to be a heart-crushing moment for him... but after one last longing look at the cabin, he instead just takes a moment to play with Katie and decides it's Worth It.Linda: I know this must be hard for you.Rick: Nah. It's easy.
- It is subtle, but the fact that Katie's romantic interest in Jade is treated as completely normal as an opposite-gender crush would be treated is bound to uplift anyone in or out of the closet.
- PAL, to her credit, before she fritters over the Moral Event Horizon, sounds like she feels sorry for Katie after reviewing her file when holding Katie captive. She talks about how they're both unappreciated by the people they care about the most. PAL also gives Katie a chance to explain why should they save a family, especially a father, that doesn't understand her.
- It seems to be the Darkest Hour at the end of the movie: Linda and Aaron have been captured, Rick is imprisoned next to Mark, and PAL has Katie in her clutches, dropping her from a fatal height. Then Rick, after talking to Mark, realizes that he needs to upload one of Katie's videos to save everyone, and begs Eric and Deborahbot for help. Pal rendered them Brainwashed and Crazy, but they realize that Rick "changed [his] programming" in their words for his daughter's sake. This gives them the means to rebel against PAL, help Rick upload the video, and save Katie before she goes "Splat!"
- Linda at the end of the movie is excited that Katie is dating Jade. She asks over a video call if Katie will invite her for Thanksgiving, saying they'd be very happy to have her. Katie is more than open about the idea.
- Before presenting the PAL Max robots, Mark tells PAL that he always thought of her as a part of his family. In the PAL Labs official website, Mark says that when he invented her, he talked to her for months while perfecting her system. Even if she eventually led a global tech uprising and almost sent mankind to their deaths, the two minutes before she really went rogue were sweet.
- A small one, but Linda saying "Hold on tight, sweetie. Mommy's got ya." to Aaron and kissing his cheek before unleashing hell on the robots is incredibly sweet. As is his smile afterwards.
- While the Mitchells are kicking ass against the robots, Mark is watching them from his cell with a fond smile.
Heartwarming / The Mitchells vs. the Machines