So far, Justice League Action has give us dance routines, Batman vs Superman fighting game matches and a very insectoid version of the Parasite. That's all been very fun, and it looks like images of a smiling Swamp Thing will continue in that vein. Or root. Whatever.
The next episode of Justice League Action will feature DC Comics' two vegetable-based behemoths punching the vitamins out of each other. Here's the official description:
When Grundy escapes his Louisiana prison, intent on using a magical crystal to raise an army of the dead from their graves, only Batman and Swamp Thing (voiced by Mark Hamill) stand in the way of his growing zombie army.
You can see the set-up for that fight in the video below, which features Zatanna and Constantine drinking and doing card tricks.
It sure looks like Solomon Grundy is singing in one of the images below. Please let that be a thing that happens.