I ran to the store and picked up a box of pineapple upside down cake, a jar of maraschino cherries, and a can of pineapple rings -- then got to work. Much to my dismay, I hadn't noticed that the mix called for a box of vanilla pudding and that's not something I have in my pantry!
Thank goodness for Google. I started reviewing posts on substitution options - several of which said there is no substitution for pudding mix but I did NOT want to go back to the store so I kept at it. Finally, I hit on a post that sounded reasonable.
For the pudding mix, I substituted:
2/3 cup powdered sugar
1 egg yolk
1 teaspoon vanilla
It was without a doubt, the BEST pineapple upside down cake ever. I will use that substitution any time a recipe calls for pudding mix.