You have got to read more on Stooge lore if you want to know why they didn't do features.

Why settle for that when there's a video of Bryan explaining the rules for 20 minutes to the Korean animators? There's also a set of rules that was sent along with advanced screener copies of the pilot.

Sure we did, Air nomad nuns appeared in Appa's Lost Days. Avatar Yangchen(last female Airbender nomad) appeared in the finale.

That's more a greeting

"Keep flamin' " would have sufficed.

Maria Bamford? Oh well then you'll love her in Korra.

His voice did mature. They had to pitch it up when he started recording for Book 3. There's actually quite a noticeable difference in his voice between the pilot and the finale.