Ficus was a running gag amongst several Creatures. The joke revolved around mistaking any species of tree for a ficus, which is actually a genus of 850 tropical trees and shrubs native to southwest Asia and the Mediterranean region.
Currently, the most infamous ficus was the one featured in Nova's playthrough of Overlord's: "Tom and Jerry: Jerry's Adventure" Minecraft map, in which he and Seamus had to "put the moves" on the ficus to complete an objective.
A ficus was also briefly mentioned in Sly's Sonic Generations playthrough when Sonic landed on a tree which Sly reaction to by saying "What the fuck? I'm on a ficus?"