If held by either parent of a Pichu when the Egg is produced, the Pichu that hatches will know the move Volt Tackle. From Generation VI onward, if a Pichu knows Volt Tackle this way (and was bred in Generation VI onward), it can be taught Volt Tackle again at the Move Reminder if it forgets the move.
In Pokémon: Magikarp Jump, Light Ball is a Friendship Item that is received as a reward after beating the Friend League. It summons Pikachu as a helper Pokémon.
Because Pikachu cannot be found in the wild in Unova, Thief and similar moves no longer permanently steal items held by Trainers' Pokémon from Generation V onward, and Poké Transfer does not transfer held items, the Light Ball cannot be obtained in Generation V outside of events.