When in the case of a sing-a-long, word game, or any other item where the title implies possession, it's grammatically correct to list the person that the sing-a-long or word game belongs to directly before their featured item which is followed by the apostrophe "s" to show ownership. As in, "Bert. And Ernie's sing-a-long." Ernie's always the one with all the fun & games. So, unless you want to say "Ernie's sing-a-long and Bert", you'll have to wait until we're talking about oatmeal. Or a paperclip collection. Then of course you'd say, "Ernie and Bert's oatmeal".
What if it's a subject that shows joint ownership like their apartment? Or their licorice? Or soda? Well, considering we're talking about Ernie and Bert here, we've all seen how Ernie works those situations out.
