The Grim Adventures of Billy and Mandy
Season 1, Episode 18: Billy's Growth Spurt
Select Source
Billy eats too much junk food that makes him feel sick. Grim prepares him a remedy using his granny's recipe, but this medicine makes a parasite to start growing in Billy's back, which Billy names Yap-yap. In the following, Billy and Yap-yap continue eating junk food, so Mandy suggest to use the antidote to the original remedy. Eventually, Yap-yap, now looking like a smaller version of Billy, detaches himself from Billy (which would have technically cured Billy without the need of him drinking the anitdote), and tries to escape from the antidote. In the end, Yap-yap drinks the antidote and is destroyed.
All Episodes - Season 1
Episode 1
Meet the Reaper
Episode 2
Skeletons in the Water Closet
Episode 3
Opposite Day
Episode 4
Look Alive!
Episode 5
Mortal Dilemma
Episode 6
Get Out of My Head!
Episode 7
Fiend Is Like Friend Without the 'R'
Episode 8
Recipe for Disaster
Episode 9
A Dumb Wish
Episode 10
Grim vs. Mom
Episode 11
Tastes Like Chicken
Episode 12
Grim or Gregory?
Episode 13
Something Stupid This Way Comes
Episode 14
A Grim Surprise
Episode 15
Beasts and Barbarians
Episode 16
Hoss Delgado: Spectral Exterminator
Episode 17
To Eris Human
Episode 18
Billy's Growth Spurt
Episode 19
Billy & the Bully
Episode 20
Big Trouble in Billy's Basement
Episode 21
Tickle Me Mandy
Episode 22
Little Rock of Horrors
Episode 23
Dream a Little Dream