The piranhas appear as orange fish after Dippy jumps up from the water. Three piranhas are visible below because one of them fell back into the water Dippy right after he jumps up.
The piranhas still appear as orange fish and can be seen swimming up to Dippy as he dancing. They open their mouths and bite him if the player doesn't flick them away. If they do, Dippy will keep dancing.
In Dippy's new minigame where you have to guide Dippy's boat with a hole in it to the island by swiping right, they appear again when the boat sinks and they eat the Dippy if the boat doesn't make it to the island, resulting in failure.
Dumb Ways to Die 2Edit
Also the another piranha group(with different color and tail fin) can be found in Dumb Ways to Die 2 the Games, which group appears around Skellieflop and Landmine Curling mini-game, the latter one is only seen in the winning result.