Some tidbits gleaned from the post-Ami Special interview (thanks to 
subtitle by VKLL):

* Ami is the favorite character of the Art Director (Junichi Higashi) and
Music Director (Yasuyuki Konno).

* Some characters were added who were not in the original storyline, notably
Chibi-Usa and Mamoru. (As well as Luna's voice used for narration)

* Often in TV there are scenes with still people (ie- with mob scenes, 
background people don't move), but more such movement was used in Ami's 
special.

* The "Number One Tutorial Seminar" (a new place in the series; where Mercurius
was) was given a deliberate mysterious look.

* There was the go-ahead for new sounds and effects as opposed to recycling
sound (as TV often does).

* A propos the steps to the Hikawa Shrine (Rei's), there were many to give the
atmosphere that it overlooks the whole of 10th street (Juuban) district.

* The Animation Director found Ami somewhat difficult to draw, especially
her eyes