Juvenile form of the couch potato
More generally: children - specifically the kind that veg out on the couch watching anime and playing video games while their physiques atrophy.
Seen on Fark.com in the thread, "TFer heard his baby's heartbeat for the first time. What life changing event happened to you today?"
"...to anyone else who is considering skipping out on their birth control, I have a few couch lizards that you can borrow for a test drive. Might make you reconsider."