After Littlefoot's mother dies, Littlefoot is comforted by Rooter, an old dinosaur who Littlefoot runs into.
Rooter: Oh, it's not your fault. It's not your mother's fault. Now, you pay attention to old Rooter. It is nobody's fault. The great circle of life has begun. But see, not all of us arrive together at the end.
Littlefoot: What'll I do? I miss her so much.
Rooter: And you'll always miss her. But she'll always be with you, as long as you remember the things she taught you. In a way, you'll never be apart, for you are still part of each other.
At one point, a group of baby pteranodons are seen fighting over a cherry. When said cherry gets eaten by a lizard, their parent shows up and gives them an entire leaf full of cherries (one for each of them) and they all fly away together, presumably to go to the Great Valley. This is sweet (and funny) enough as it is, but the REALLY heartwarming moment is when the blue pteranodon sees a visibly upset Littlefoot lying on the ground nearby. What does he do? Offer to share his cherry with him! After arguing over a cherry with his brothers and sisters, the little guy is perfectly willing to share it with a complete stranger in an attempt to comfort him. Awww!
When all five main characters fall asleep together in a pile.
Littlefoot could let Cera smash her head in while trying to get her own food. Instead he grabs a handful, waits, and throws a portion down after she rams her head against a tree. He'd rather see her confidence boost than let her starve.
When they all finally made it to the great valley.
Bonus points for the moment when Ducky introduces Spike to her siblings, who are all more than happy to accept him into their family.
That, and the part where all the kids are together again just before the end credits roll.
What's the first thing Mama and Papa Sharptooth do when they find Littlefoot's foot stuck in a log while Chomper is trying to help? They snuggle their baby!Bring on the cavities and the hatedom...
For some reason, Spike taking an immediate liking to tickles (an early mammal from the 4th movie) is really adorable. Especially as they're the first to find the night flowers together.
Also from the Fourth movie and relating to Spike, he finally says his first word: "Ducky". It's even more heartwarming because he does this to wake her up so she isn't eaten by Dil.
In the 5th movie, Chomper seems positively overjoyed to finally have friends on his island, and does everything in his power to try to keep them safe and happy.
"We live in a whole other world and we miss it. But we'll always be friends Chomper."
Petrie's Uncle Pterano finally owns up to his mistakes, and tells Petrie that he will endure banishment, but will dearly miss him.
Mr. Threehorn calling out Hip's father in the third movie. Especially Mr. Threehorn, since he's clearly reliving his own Heel Realization and apologizing to Cera when saying it.
The end of the The Big Freeze, where Mama Swimmer saves Spike from drowning in the icy water. If his cry of "Mama!" doesn't get you, the exchange that follows after ("You saved him!" "Of course I did, he's my boy") will.
Tricia's birth in movie twelve. She's just too cute...
Even more cute, she says her first word at the very end: Cera.