Despite what the show frequently implies with Pikachu's attacks, electrical attacks can NEVER harm ground types.
In one episode, an Exeggcute evolves into an Exeggutor without
a Leaf Stone. This Pokémon requires the Leaf Stone to evolve - it can not evolve through experience points.
In an early episode, Flint (Brock's father) says that Brock's mother passed away. In a later episode, Brock's mother is actually in the episode alive.
That makes Flint (Brock's father) a liar.
In one episode Brock's Geodude participates in an all-Fighting Pokemon tournament. A Geodude, however, is NOT fighting, it's rock/ground. In the original card series there was no rock or ground type, only fighting type to represent all three types.