The Brave and the Bold #122 (DC, 1975 — Cover A)

"THE HOUR OF THE BEAST." Batman is shocked to find the Swamp Thing in Gotham City, put on display by carnival owner B.B. Riggs. Batman demands that the Swamp Thing be set free, but Riggs refuses. Gotham City meanwhile is suddenly swarmed by giant roots that have sprouted from the ground. These roots come from seeds that have been dumped in the city water supply and grow to alarming sizes once exposed to the air. During the chaos, the people of Gotham City blame the plants on the Swamp Thing, and the government uses this as a moment to try and capture him for examination. Batman gets in the middle and frees the Swamp Thing and asks for his help in dispelling the roots.