Just watched Suited for Success with the commentary. Highlights:
1. Tabitha St. Germain apparently has a pair of glasses really similar to the ones Rarity wears.
2. Rarity's voice is at least partially inspired by
Audrey Hepburn.
3. As you know, "Art of the Dress" is heavily inspired by "Putting it Together", but apparently Daniel Ingram had never heard that song before until he was told they were using it as a reference. He also has to re-record the song three times: the scratch track was recorded with Pinkie's singing voice, then it was re-recorded with the singer who did Twilight's singing voice (because she was originally Rarity), but when they switched her to being Twilight's singer, they had to find someone else to do Rarity, so they had to re-record it with her. Daniel Ingram said he got really sick of the song.
4. When DJ-
PON 3 appears, paraphrased from memory: "There's the DJ Pony. This is the only time she appears in the first season. WHAT COLOR ARE HER IRISES!?"
5. An interesting bit on the relationship between voice acting and animation: When the voice actors really get into it, they inspire the animators to add more nuance. The example was Rarity's breakdown scene, her little sobbing thing at the end wasn't originally storyboarded that way, but Tabitha's performance inspired them to animate the character differently to match the voice.