"You used the Prescription and received an Eyeball Frog! Be quick and deliver it to Lake Hylia while it's cold!"
— In-game description
The Eyeball Frog as it appears in-game

The Eyeball Frog is a quest item from The Legend of Zelda: Ocarina of Time. Part of the quest for Biggoron's Sword, the Eyeball Frog is a frog with over-sized eyes. It is given to Link by King Zora XVI, who tells him to take it to the Lake Scientist in the Lakeside Laboratory in order for Link to prepare the World's Finest Eye Drops for Biggoron.

The frog cannot survive long outside its natural habitat and will die if Link does not make it to Lake Hylia in time. It cannot be taken into Death Mountain Crater as a shortcut due to the frog's intolerance to the intense heat, nor can any warp songs be used to make the task go faster (as with all timed tasks of the quest), as both attempts will cause the frog to die immediately. Upon giving the Eyeball Frog to the Lake Scientist, Link will receive the World's Finest Eye Drops.

Humorously, the Lake Scientist at first mistakes the Eyeball Frog as a present, as it is considered a delicacy.