I only saw the first six Land Before Time movies, as a kid. All the movies from here on out are movies I've never seen before.
Stone of Cold Fire is a bit of an odd duck. The animation is different, and it kept bothering me that the characters didn't look the same as the other movies. Ducky changed sizes a few times, Cera lost some detail, and was Littlefoot always that color? There were also a few moments with blurriness and pixelation, too, which looked bad.
I'm guessing they switched to computer animation, because the movie also contained a few neat 3D animation effects. Mostly, the scenery spun around Pterano as he talked.
The story is that Littlefoot sees a comet land, while everyone else is sleeping. Everyone gets up in arms about this "stone of cold fire", because it might have magical powers. That's what a pair of mysterious Rainbow Face dinosaurs say, at least.
Enter Petrie's uncle, Pterano. He's a villain, who tried to declare himself king a few years ago. He wasn't a very good king; he tried to lead some dinosaurs to safety, but they all got eaten. Pterano was exiled after accidentally killing half the herd. Now he's back, and he thinks the stone's magical powers will make him a better king. He lies and even kidnaps someone, to get his hands on the stone.
Halfway through the movie, it is decided that Pterano isn't evil; he's just misguided. Kidnapping? Manipulation? Leading people to their deaths? Nah, those aren't indicative of his character. Deep down, he's just a nice guy, with minor delusions of grandeur. There's even a musical number about his delusions of grandeur. I thought that was odd.
Most of the movie is spent, trying to reach the stone of cold fire. Turns out it isn't magical at all. It's just a crashed meteor. Pterano is exiled a second time, although his sentence is lessened because he helps save the kids.
As for those Rainbow Face dinosaurs? They secretly follow Littlefoot the whole time, and help him a bit. The end of the movie reveals that they are ALIENS FROM ANOTHER PLANET. They go away, and Littlefoot keeps their secret. It was incredibly unexpected and weird.