Allison Janney (Bonnie) & Octavia Spencer (Regina) also worked together on The Help (2011) as Charlotte Phelan & Minny Jackson respectively.
There is a disguised mark on the sidewalk right where the buss doors stop when it stops to let Bonnie and Chrisi off.
Marks allow the action to stay in camera frame as the director wants to see it.
The song "Jackson" is also featured in the movie The Help, which starred Alison Janney and Octavia Spencer.