|Born||In c. 282 AC, King's Landing|
|Died||In 283 AC, King's Landing|
|Book(s)||A Dance with Dragons (mentioned)|
"Pisswater prince" is the moniker that Tyrion Lannister gives the nameless tanner's son from Pisswater Bend who, according to Illyrio Mopatis, was swapped with Prince Aegon Targaryen when he was an infant.
His mother died birthing him and his father sold him to Lord Varys for a jug of Arbor gold - his father had other sons but had never tasted Arbor gold. Varys gave the pisswater prince to Princess Elia Martell and carried Aegon away for his own safety. 
During the Sack of King's Landing, Ser Gregor Clegane scaled Maegor's Holdfast and entered the nursery of the infant Prince Aegon Targaryen, son of Prince Rhaegar Targaryen, and killed the baby present by dashing the boy's head against a wall. He then raped Elia, his hands still covered with the blood of the murdered baby.
A Dance with Dragons
Travelling down the Rhoyne aboard the Shy Maid, Tyrion Lannister manages to puzzle out that Young Griff might in fact be Aegon Targaryen, although he has not managed to figure out how he managed to survive the events following the Battle of the Trident. Aegon discloses to Tyrion that as an infant he was swapped with a tanner’s son from Pisswater Bend.
The girl had been recognizably the Princess Rhaenys, but the boy ... a faceless horror of bone and brain and gore. None of us looked long. Tywin said that it was Prince Aegon and we took him at his word.—thoughts of Kevan Lannister
- A Dance with Dragons, Chapter 22, Tyrion VI.
- A Storm of Swords, Chapter 11, Jaime II.
- A Game of Thrones, Chapter 3, Daenerys I.
- A Game of Thrones, Chapter 64, Daenerys VIII.
- A Game of Thrones, Chapter 12, Eddard II.
- A Game of Thrones, Chapter 30, Eddard VII.
- A Storm of Swords, Chapter 70, Tyrion X.
- A Clash of Kings, Chapter 17, Tyrion IV.
- A Dance with Dragons, Epilogue.