Disclaimer: Percy Weasley, the Ministry of Magic and Mr. Crouch all belong to JK Rowling.
Percy was quite excited to start his new job.
His first own job. He'd work hard, and he'd be the best sub-ordinate ever.
He knocked on the door. Mr. Crouch, his new boss, was sitting there.
"That Weasley! Another memo about Muggle electicity! Hmph."
His new boss looked up.
"So, you're... what was it again? Weatherby?"
Percy's mind raced. This man didn't seem to like his father too much...
"Yes, Weatherby. Percy Weatherby, Sir."
"Well, there seems to be a mistake in your forms, over there... I think they got your surname wrong..."
"I'll correct it immediately, Sir!"
He nearly jumped. He didn't want to be "That Weasley"'s son. Not if his new boss spoke about his father in that tone of voice. He wanted to rise in the Ministry, and have enough money for his family. He didn't want to be stuck in a junior position forever, because people didn't like his father. He calmed his conscience with these words, that this would benefit the family he'd just denied for the first time.
With a wave of his wand, he changed his name on the forms to Weatherby. Percy Weatherby.