Entrances can be a very important part of setting up interest in the characters for young children. Think about how much kids all over the world love their favorite WWE wrestling superstars. So, for the proposed YOUTUBE show opening a few basic ideas:
Koala slides down a tree.
Kangaroo jumps in.
Croc rushes out of water.
Wombat comes out of a cave.
Platypus well she has 2 options.
Bandicoot ~ not familiar with bandicoots. Any ideas here?
Anyway, I'm sure other posters here, both positive and critical, will have better ideas.