It was hinted at, but early this morning Nintendo finally confirmed that Super Mario Odyssey would have co-op play. Revealed during the last day of Treehouse Live the second player will control Cappy.
Cappy will fly around Mario controlled by another player, protecting him and completing puzzles. Nintendo this is a way to introduce players to Super Mario Odyssey and to video games themselves.
You can see it in action at 1 hour 47 minutes in.
Or in the office, we won't judge
Definitively done with the Wii U now.