Ok I'm not going to do any drawing from it cause I really don't like the scene much and it really upset and freaked me out as a kid, and it p****s me off.
But I'll describe how I think the fight between Littlefoot and Cera would have gone with Bambo there.
Well of course I can see Bambo disapproving of what Cera says about Littlefoot's mum. E.G. saying "Cera!" in a shocked tone. And been horrified when Littlefoot lashes out at her and go tumbling down the hill.
I can well picture him hopelessly shouting for them to stop and that fighting would solve anything. Then when Littlefoot supposedly bites Cera when she says "Let go of my leg!" shouting "No Littlefoot please don't do that to her!"
Then he runs in-between them yelling " Please STOOOPPPPP!" Then gets rammed by them both.
When the fight is finally over and Littlefoot shouts. "Go on! Go the wrong way! We never wanted you with us anyway!"
Bambo says "Oh please, Littlefoot don't say that." Then Littlefoot says " Oh, so your siding with her!" And he walks off. And Bambo is like " Littlefoot no I. I. * grunts angrily and kicks the sand in his anger* Fine! If that's what you think, I'll go with Cera! " I mean I've tried to be your friend this whole time and I felt sorry for you, and this is how you thank me!?" *Storms off in the way Cera is going*
I can also see him getting a bit snappy with the others.
Ducky: Are you alright Bambo?
Bambo: No! I've just been rammed by my friends, and Littlefoot has accused me of favouritism! Of course I'm not alright!
Petrie: Oh Bambo please don't go.
Bambo: No my mind is made up Petrie! I know what Cera said was wrong! But I am not staying with someone who attacks my best friend and doesn't appreciate it when I try to help and feel bad for him!
Here is Bambo with Cera, Petrie, Ducky and Spike when they go the wrong way.

If your wondering why Bambo is at the front, I have an idea that as he's a fellow three-horn, Cera let's him take the front cause secretly she's scared too and wants her long time male friend to be in front to protect her.
In this one Bambo and Cera have in the cave just before the dome-heads show up, and Bambo as he's been at the front of the line, has only just noticed that Petrie, Spike and Ducky aren't with them.
