Some of the wishes on Star Hill are this. Special note goes to Luigi's wish. I wanna be a great plumber like my brother Mario. Another notable one is from Mallow's parents, wishing for him to come home. You know what's sweeter? They both came true.
And it's especially heartwarming in the case of the latter wish because it came true even with the Star Road out of commission.
The music playing in the background takes this Up to Eleven.
Bowser's Pet the Dog moments in Monstro Town where he meets deserters from his army and wishes them well in their new lives after they apologize for fleeing. Who knew Bowser was a Benevolent Boss?
And let us not forget the rather heartwarming and awesome moment where you find a female chain chomp imprisoned in Booster's tower. Bowser not only manages to calm her down and befriend her just by staring at her and offering her a few gentle words (even asking Mario to look away from her while they're talking as she's apparently very shy) but convinces her to come along as Bowser's first new weapon. Who knew Bowser was a Chomp Whisperer?
Many fans find this scene so heartwarming they refuse to sell the Chomp to a merchant even after Bowser gets better weapons; they just keep her in their inventory.
A minor one in his normally hilarious weapon Hurly Gloves, where he forgoes the doll entirely to toss Mario himself at the enemy... unless Mario is knocked out or under any status effect, in which case Bowser will not lay a finger on Mario, instead using the doll like he was supposed to.
After successfully defeating Valentina and Dodo, Mallow rushes to free his parents from inside the palace. Mario is left outside, and after a moment, he pulls out Princess Toadstool's umbrella. Why does he do this? Well, whenever Mallow cries, it starts to rain...and Mario realizes that Mallow is finally about to meet his parents for the first time in his life. There will definitely be happy tears at that moment. It's also likely safe to assume that Mallow's ability to create rain when he cries isn't limited to just him.
After recruiting Geno into your party, you can return to the inn in Rose Town, where Gaz will be ecstatic to have a chance to talk to his hero. Geno tells the little boy that unfortunately he can't stick around to play with him, but promises he will return once his business is finished. And far from being a poor sport about it, Gaz gives Geno a Finger Shot to take with him and wishes him luck. Sadly, viewing this cutscene is optional, and the ending of the game plays out as though you hadn't seen it, meaning Geno will always head straight back to the Star Road once Smithy is defeated. However, it's entirely possible Gaz could simply wish on a star for Geno to come back and play.
Using Mallow's "Psychopath" move on the Magikoopa in Bowser's Keep reveals that he is Kamek, who is seemingly disturbed by having to fight Bowser, who his thoughts refer to as "my child." Aww.
Even after finding his real family, Mallow still considers Frogfucious as his grandpa.
When Valentina is defeated, she winds up in Booster Tower, where she's a Jerkass at first, but then Booster whispers something to her...and then they're seen getting married in the post-credits sequence. (Though Booster ends up getting cold feet at the last minute.)
Your allies actually thank you when you heal them during battle. Yes, even Bowser.