This could be an interesting idea, although I'm not sure exactly what this would involve. What would the characters talk about, exactly? 
Their experience working on the show, what it was like to do 39 whole episodes, the process of writing some storylines and the whole change in Season 3. Here’s some examples:
1. Bigwig: I have to say some of my best moments are the ones where I really get to let loose and shout out my lines in a certain situation *show clip of bigwig tackling vervain to the ground and yelling at him from escape from Efrafa*
2. Woundwort: For me, anytime a scene calls for me to threaten someone in a booming voice, that is a great time for me to sound like serious business will happen *show clip of Woundwort telling Hazel to surrender from the homecoming*
3. Narrator: even though the show got 26 episodes using elements from the book and having some cool down filler episodes, some fans of the previous versions weren’t too pleased with the more toned down storyline. So with the third season, the show decided to get a bit darker to try satisfying some of those fan’s thirst for a action packed Watership Down again.