Thanks to a post from @powerbook_pete on Twitter about Alton's 'sister' Marsha being in a Pepto Bismol commercial, I went looking on the ol' internet to see if I could find it. Still looking for that one, but I did find a great compilation of Marsha Brown-Brady appearances on Good Eats posted on Youtube by Merrilyn Crouch herself!
p.s. If anyone finds that Pepto commercial, feel free to frop the link in the comments section here or post to @altonbrownnews on Twitter. Thanks!