I've noticed that Littlefoot was the only one that stuck around to go back to Chomper. He was the one who named him. He tried to take care of him and stood up for him when even Ducky was thinking they should let him just go away.
Also, Littlefoot was the only one who went after him when after Chomper's parents were driven back.
Also, it seems that Chomper kept the name Littlefoot gave him (despite the fact Chomper's parents probably wanted to name their own kid rather than somebody else.). How Chomper was able to avoid bringing up Littlefoot as to where he got the name "Chomper" is a mystery. If he had mentioned Littlefoot earlier, one would have thought that Chomper could easily have just mentioned it in film V and they wouldn't have had to hide in the Stinky Place. On the other hand, if his parents had mentioned a desire to eat Littlefoot, there is no way Chomper could be as naive as he was in the fifth film either.
Another strange thing is that Chomper says Littlefoot's name first when he sees the Gang of Five on the island and talks to them. He doesn't mention any of the other's names but Littlefoot's at first. (I'm wondering that had he encountered the Gang of Five minus Littlefoot, if he'd have let the others walk away. After how the others were to him in the 2nd film, he might not have as fond of memories of them as Littlefoot.)
Also, Littlefoot goes after Chomper (the others don't bother it seems) in film V when Chomper goes into the water (a great irony that Littlefoot went, as, as those like Ducky123 argue, that Chomper will one day hunt Flatteeth (not my belief, but theirs), and so one wonders if Littlefoot knows that won't happen. And, of course, we all know what happened to Mama Longneck too. Another irony.) and saves him.
I think I can safely say that Littlefoot is the closest of the Gang of Five to Chomper and perhaps one of the closest out there to Chomper period (other than maybe Ruby as a rival).
