The Conqueror: Four of the Planeteers are fooled by Zarm and choose him over Gaia. Tearjerker ensues - until Gaia comes to the kids as a mortal and shows them what Zarm is really like. The scene where they apologize definitely makes up for that, though. Especially that part where Gaia hugs Gi and kisses her forehead. And it gets even better when they confront Zarm...
When Wheeler stops his more recent past self from stopping his more distant past self from accepting the Fire Ring, and explains the Aesop to him(self):
Rebelling!Wheeler: I never thought of it that way. Reformed!Wheeler: I know. (quieter:) I just hope it's not too late to save Gaia.
And finally, after Captain Planet changes the villains' time trip's direction:
Captain Planet: They're in for a real future shock. Wheeler: Can't be any worse than the shock I had there. Gaia: Don't worry, Wheeler. Wheeler: GAIA! You mean you're not...? Gaia: Now that you're a Planeteer again, I feel just fine.
Also, the scene when the other Planeteers appear and reveal what they did to save Wheeler from the cave-in; especially in Linka's case.
Linka: I would do the same for anyone... (suddenly clings to Wheeler) Oh! You had me so worried!
Heat Wave: Upon returning to Hope Island, the Planeteers find Gaia very sick and weak. The interesting thing is that the one to cradle her caringly is neither any of the Nice Guys: Ma-Ti or Kwame, nor any of the girls. It's Wheeler.
Summit to Save Earth, Part 2:
When Gaia is getting transformed back to her normal self, Linka is the first to run and cling to her, with Kwame, Gi and Ma-Ti very close behind.
When escaping Zarm's spaceship, Wheeler, Ma-Ti and the girls run ahead, while Kwame is briefly shown staying behind to help Gaia walk.
In general, Captain Planet and Gaia don't have much screen time together, but in this episode, while getting rid of Zarm, the Captain manages to give Gaia a quick, yet very affectionate hug, which doesn't go unnoticed by Kwame and Wheeler.
The Great Tree Heist: Captain Planet is so badly injured by Greedly that he is unable to be summoned, leading to the Planeteers thinking he's dead. Later, Captain Planet is summoned in time to save the Planeteers from being killed by Greedly. After getting them to safety, Gi and Linka jump out of the Geo-Cruiser and run into his arms. Captain Planet hugs them back, looking like the happiest person alive.
A Mine is a Terrible Thing to Waste, Part 2: Gi is helping an injured Wheeler as the group leaves a cave. She reveals that her love for sea creatures (especially dolphins) has been part of her since she was a little girl and tells him of a time she was friends with a dolphin named Tisa, that she was forced to leave behind. A year later, she came back to find Tisa dying due to the ocean being polluted, which devastated her. In present day, she vehemently states that she made a vow that she'd never let a friend down like that again.
Linka tells a similar story. As a young kid, she and her grandmother raised canaries which served in the mine as gas-detectors. She didn't find it fair, however, that they were dying in mine-related gas leaks; the sorrow she felt about one of them prompted her to dedicate her life to protecting birds.
Missing Linka: Linka spends most of the episode running around by herself. While she's inside a mine, she falls and gets knocked unconscious. She's saved by a mysterious bundled stranger (not for the first time that day either), who runs away after she comes to. It's later discovered that the mystery man is none other than Wheeler. She even kisses him for the first time to thank him.
'Teers in the 'Hood: Wheeler not only talks Gi out of outright killing the guy who shot her friend, but even hugs her as she is crying into his chest.
No Place Like Home: The Planeteers happily swarming over Gaia when they finally find her... and then again, on Hope Island, once they're all safe. The first time they do this, Captain Planet even calls it a "family reunion. Sort of".
Dirty Politcs: In the possible future, we see MAL gaining a Morality Pet in Dr. Blight's daughter Betsi, who is by far sweeter and more heroic than her mother to the point that she actively tries to help the present and future Planeteers stop her mom from becoming president. MAL tries to pull a Heroic Sacrifice at one point to save Betsi and ends up doing a full Heel–Face Turn.