These are the confirmed things in FusionFall thats Chowder related.
In Goat's Junk Yard,the signs show Mung Daal.
A Chowder Hat is obtainable.
A Chowder Nano is possibly going to be in FusionFall.
Chowder was in the game for the christmas (knishmas in the show) & new years event, and returned with Shnitzel for the birthday bash event (alongside characters like Flapjack, T.O.M, Zak Saturday, etc.)