First series, episode nine, has Jackie poisoned with a toxin that's going to slowly petrify him, unless he offers to exchange the Talismans for the antidote — he refuses to consider it. Jade is not so accepting, and they end up sitting in a park after dark with her begging him to make the deal. The phrase "I don't want a boulder for an uncle!" was a lot more heartwarming than it honestly has any right to be.
When they're not driving each other to distraction (which is most of the time), the Chan family in general tend to pull out a good few CMOH.
Any time Uncle shows a member of his family or Tohru affection, showing that he's not just a grumpy old geezer and genuinely cares about them. Like the episode when Uncle gets the Dog Talisman. "Jackie, thank you for allowing me to re-experience my youth."
Several of Jade's exchanges with Tohru post season one are surprisingly sweet considering there was a point not too long ago when he would've quite happily cut her open to get a Talisman out of her. By the time the third series rolls around anyone who even thinks about hurting Jade in his presence had better watch out.
A particularly sweet example comes from "Demon in Di-Skies", the (in)famous episode where Hsi Wu disguises himself as a boy Jade's age to get his enchanted tail back from Uncle. Jade is implied to have a childish crush on him, and feels upset when the truth is revealed. Lamenting to Tohru that it was nice having someone around who listened to her, she realizes Tohru already fits the bill and gives him half of her Yin Yang necklace.
Jade: (to Tohru) Yin and yang. Big and small. Me and you.
Jackie's reaction to Captain Black's hospitalization at the hands of Valmont and the Dragon talisman is part this, and part scary.
During the "Demon World" two parter, Jackie grows despondent after losing the Ox talisman. Thinking that unlike the rest of the J-Team, he is useless without Super Strength (this due to the fact that this universe's Jackie never having learned martial arts). Jade gives him a pep talk about how he never even liked using the talismans before the change in the timeline. She also tells him that he was a great warrior and can be one again, with a little retraining.
After El Toro is cursed to become the next Chupachabra, they're forced to leave him tied up in a cave while they head off to find the cure. Paco takes a moment to look back at him, and El Toro smiles.
In one of the later episodes, it's revealed that Jade not only becomes head of Section 13 later on, but is also extremely skilled in both martial arts and chi magic. When Jackie asks her at the end of the episode how she turned out so well, she simply looks at him and says "You, duh."
When Paco turns evil due to the Oni Mask, El Toro tells him to remove the mask, which gets through to the real Paco. Paco says wrestlers can't remove their own masks. El Toro, who always boasts that he never removes his mask, takes off his own so that Paco will remove his.
The final episode contains one. Drago is getting sucked into the portal back to the Demon World, and asks Shendu, his father he was just fighting and planning to betray, for help. The heartwarming part is that Shendu helps his son, but then Drago fools him and then they're both trapped and start bickering. It was a nice gesture.
In the last season, the Earth and Moon Demon chi are both activated on Jade's birthday. While the Chan Clan is at a zoo trying to find the Moon Demon chi, Tohru gives Jade some cotton candy as a birthday present.