You can change three things in Harry Potter and Twilight.

Harry Potter: Dobby didn't die, Fudge wasn't so annoying, and Drarry happened.

Twilight: I only have one thing I would change - that it was never written.

Twilight:
1. It needs a better plot.
2. All the characters are Mary-Sues. That should be fixed.
3. It should just be completely rewritten by somebody who is not Stephanie Meyer.

Harry Potter:
1. Fred, Remus, Tonks, and Dobby don't die.
2. Hufflepuff gets the glory it deserves.
3. Luna is the new Ministress of Magic and everybody realizes the existence of Nargles and Crumple-horned Snorkacks.

Twilight: Get a plot. I would change many, many things, but most of all it needs a plot.

Harry Potter: The entire Epilogue. I would explain more what happened to the characters after the story ends.
Luna and Neville would get married. :)
And lastly, I'll voice what we all wish: Fred wouldn't die! He SHOULDN'T die! That's what needs to be changed.

Harry Potter:

1. Add another chapter right before the epilouge that covers the events following the battle, and explains more about the characters in their adult lives.

2. Dobby and Fred survive.

3. Include a a scene where Dumbledore announces to the school Gryffindors are superior to all the houses, especially Huffelpuff.


Twilight (only three?)

1. Give it a plot

2. Give the characters a personality

3. Have Rowling re-write it.

some pairings, death of hedwig :(, and the 19years later thing was a bit weird i reakon it should have been like 3years later