Some background ponies that I noticed in the noir bar scene in “Sparkle’s Seven”.
The one on the right, is a ponified Betty Boop. The one on the left with the top hat is a ponified Marlene Dietrich.
Here’s a link to the 2017 Google Doodle page for her:
https://www.google.com/doodles/marlene-dietrichs-116th-birthday
A few seconds before this frame, the Marlene pony winks at Betty Boop.
After Rarity and Dash come in asking for someone with information, Marlene’s cutie mark is revealed to be a top hat. It’s seen as she’s bolting out.