Dandelion of Doom

The Dandelion Of Doom  (Full name being The Deliriously Dangerous Death-Defying Dandelion of Doom) was the unintentional result of George and Harold pouring the growth juice they stole from Zorx, Klax, and Jennifer out the window in order to foil their plan of making the zombie nerds bigger and more evil than they already were.

It is voiced by Len Forgione in the Sound-O-Rama Audiobooks.

Captain Underpants and the Invasion of the Incredibly Naughty Cafeteria Ladies from Outer Space (and the Subsequent Assault of the Equally Evil Lunchroom Zombie Nerds)
The Dandelion of Doom is an ordinary dandelion turned evil on accident by the growth juice poured out the window by George and Harold. We first see the dandelion when Captain Underpants uses his cape as a parachute, since attempting to swing onto the ground using toilet paper hadn't gone as planned.

As the three are parachuting down, they unfortunately land near the overgrown and evil dandelion, with the captain getting himself caught between the jaws of it. Thankfully, the boys give the captain Extra-Strength Super Power Juice in order to defeat the dandelion, which he eventually does. The Dandelion of Doom only appears in the third book, as it's defeated in the same book as well.

Captain Underpants: The First Epic Movie
The Dandelion of Doom makes a brief cameo in the end credits.