Ted, Gary and Evelyn were plants Mark Lilly used to own. Mark shows their photos to Randall Skeffington when Randall has turned into a plant, in the episode "Little Ship of Horrors", to show how bad he was at keeping plants. Mark says he's "killed every plant [he's] ever owned."
Ted was a ficus Mark had in college but he killed him before Thanksgiving break. Gary was a cactus that died because Mark let him dry out. Evelyn was a flower which melted since Mark let her sit in the sun for too long, as she's plastic.