The Tadpoles are an optional character encounter. You find them after solving the puzzle that fills the underground river with water. You are not required to talk to them and can safely ignore them without having much impact on the main story.
Responses[]
The Tadpoles give responses to the player upon the amount of times talking to them: (Normal Difficulty)
1. "My dad's dead."
2. "A snake ate him."
3. "You killed him."
(Extra Difficulty)
1. "My dad's dead."
2. "A snake ate him."
3. "He was looking for a home to go back to..."
4. "He can't even go back to the earth now."
5. "Who killed him?" "You killed him."
After the last response, the tadpoles will cause tiles you are standing on to break apart, causing Viola to fall into the water and meet her demise (supposedly in the form of drowning, although the Tadpoles could have had something to do with her death, beyond just breaking the tiles she was standing on).
Fate[]
After you wash the Red Shoes in the river in order to obtain the Glass Shoes, interacting with the tadpoles garners the message: "Dead Tadpoles floating in the water."
Interacting with them in Extra Difficulty Mode when you have washed the shoes will kill Viola.