So, I'm rewatching the first Ice Age, and then I realized something in the film. Starting at 43 minutes to about 46 minutes in the film, the three main characters (and the baby) gets stuck in a cave. When trying to find an exit out, Sid gets separated from the others. The side tunnel he takes has frozen animals in the walls (like a museum). First it's a fish, then a dinosaur, followed by evolution. Once back with the group, they see a UFO.

Then when you look at Ice Age 2 (the Meltdown), Ice Age 3 (Dawn of the Dinosaurs), Ice Age 4 (Continental Drift), and Ice Age 5 (Collision Course). The theme follows a similar pattern.

In the second film, main (secret) villains are fish like monsters. The third is of course, dinosaurs. Fourth involves a Gigantopithecus (part of the hominidae tree (evolution)). And then the 5th film involves an asteroid that is about to hit the planet.

Is this just happened by chance? Or did the creators did this on purpose?