The little Slice of Life sections from the dance segments in Spring Carnival. For longtime viewers of the series, seeing some of their favorite characters in their own settings really brings home the nostalgia factor. Here are some examples:
Splash☆Star: Saki and Mai are losing a volleyball game but are spurred on by their cheering friends and are able to turn the game around. The girls then engage in a celebratory hug. And for meta-Heartwarming points, the cameo appearances of Michiru and Kaoru as Cure Bright and Cure Windy.
Fresh!: On top of bringing back the first ED theme, which alone can count as a meta-Moment of Heartwarming, the Cures are seen giving hearts to many of the side characters, including their families, Kaoru, Westar, Soular, and some of Labyrinth's children. After the dance, Love says that while Setsuna has been absent for a while due to reforming Labyrinth, she, Miki, and Inori still consider her to be their precious friend. Setsuna smiles in response.
HeartCatch!: Cologne, Yuri's long-forgotten fairy partner, is shown on-screen for the first time since 2010. Even Yuri is moved to tears.
Suite♪: Ako smiling with the purified Noise and giving her mom a bouquet of flowers, followed by the rest of the Cures jumping in for a group hug. Hibiki playing piano with both her mom and dad looking on can also be one due to how little time either can spend with their daughter.
Smile!: Miyuki and the gang get together to celebrate Candy's birthday. Needless to say, there were smiles on both sides of the fourth wall.
DokiDoki: Rather than a Slice of Life segment, DokiDoki plays a montage of moments from its run, including Aguri and Eru holding hands in the festival episode and Mana giving Regina a hug during the final battle.
HappinessCharge!: Megumi and the others hold a "Happiness Party", complete with the flowers cut to look like Ribbon and Glassan and Blue making an appearance, presumably to visit the Cures after helping Red restore his planet. Yep, there's plenty to be happy about.
The ending to Everyone Singing - Miraculous Magic finally has Cure Echo join in the Dance Party Ending.