Unexplained Parent missing from entire story.
This was a massive annoyance for me when watching Pokemon as a kid, infact the lack of fathers in General was very strange.
For Example Ash(Father), Misty(both Parents), Brock(Mother), Gary(both Parents) had missing Parents that at no time was ever explained, some people suggest there was some kind of war but even that isn't explained.
If someone is missing then fair enough but explain, it lacks depth in the characters especially in shows that last very long and still don't bother.
In basically every Pokemon game as well the father is missing.