1. Random weird characters.
Like Charles the Potato sends a message to Harry. The heck?
2. Harry's Quadruplet Little Sisters
How does Harry have a younger sister when his parents died and were not noticed? You know, 4 babies crying?!?! How did Hagrid and Dumbledore not notice the 4 other younger babies just crying there?!?! This bothers me like all heck. Maybe a twin, older sister, or one younger sister, but not 4. Not 4 babies.
3. The Hogwarts students dancing to the modern songs.
They're not dancing to the Gangnam Style in 1991. Gangnam Style was released in 2012. Nice try, fanfiction writers.