For your animation pitch you need to think about the following:
Medium/Format: is this a short, a TV series, a kids TV series, a feature film, a web series?
Overarching story: What is the situation - what's going on.
Setting: Where is it set - some fantasy realm, Cambridge, Long Road?
Main characters: Who are the stars?
Supporting characters: Who else populates the world?
Target audience: Who are you hoping will watch this? What other animation do you think
Here's a few in interesting links to think about.
This is how Dan Harmon comes up with ideas for his sitcom Community - in terms of narrative.
http://www.wired.com/magazine/2011/09/mf_harmon/
And here's some interesting ideas on creativity and creative process:
http://criticalperspectives.posthaven.com/brainpicker-26032011-2140