Contains the first reference to the character Swamp Thing existing in the Arrowverse. The character has had multiple live-action adaptations, with the most recent - the short lived 2019 TV series Swamp Thing (2019) - previously being established as being set in another universe.
This is the second time Swamp Thing is mentioned or shown in the Arrowverse. The first being Crisis on Infinite Earths: Part Five (2020).