Heartwarming / The Lightning Thief

• Sally and Percy's devotion to each other in "The Minotaur". If "Strong" didn't get it across to the audience that they love each other like hell, this will. Percy, a teenager with little fighting experience, blindsided by the appearance of another terrifying monster like the one he was told was a delusion, refuses to leave his mom alone. And Sally, a thoroughly human woman who knows exactly the caliber of danger she's facing, tries to convince him to run and let her protect him.
  Sally: Over here! Yeah, you! You want my son, you have to answer to me!
• After "Another Terrible Day", Grover tries to apologize for not protecting him well enough the previous night, clearly feeling the insecurity of his failure with Thalia. Percy cuts him off by throwing his arms around Grover and saying, "I am so glad you're here."
• Luke comforting Percy after "Their Sign" and "The Oracle". Even better, he knows exactly where to look for Percy and sits down quietly with him, allowing him to talk out his feelings about everything, complete with Held Gaze. The fact that he tries to convince Percy to join him after his Motive Rant implies that, unlike in the book, he wasn't faking his affection for Percy and genuinely feels for the sticky situation he's in.
• "The Campfire Song" is chock full of these. The whole atmosphere is that of a tired family shooting the breeze together.
  • Near the end of the song, Percy, fresh off confessing that he believes his dad left because he simply didn't think Percy was worth it, wanders away from the fire, looking pensive and unhappy. Luke takes notice and wraps an arm around him to pull him back to the circle, while singing, "I don't care where our parents may be as long as you are here with me."
• "Son of Poseidon" is largely a rollicking fight song, but as Percy is preparing to go up against a god, he hugs both Annabeth and Grover and delivers these lines:

  This could be the end, but I ain't sad, 'cause you're the two best friends this screw-up ever had.

  • Deleted song "Try" has a similar sentiment in the bridge as the trio tries to comfort each other amidst their anxiety about the high-stakes quest.
    Grover: I'm not leaving your side until we find what matters.
    Annabeth: I'm not leaving your side until we're back home.
    Percy: I'm not leaving your side until you're remembered.
    Together: No matter how far we have to go.
• Also in "Son of Poseidon", there's a subtle Symbolism in the melody of the song. In the beginning, it was likely gonna be a reprise of "Good Kid"; Percy expressing his Heroic BSoD and his temptation to sacrifice the world for the return of his mother and safety of his friends by handing the Master Bolt to Hades. But then Sally begins singing:

  Sally: What belongs to the sea can always return.

  Percy/Sally: What belongs to the sea can always return...

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