Harry didn't know his aunt was a witch until she took off for a ride on her broomstick. Harry was also surprised to find that his aunt could turn into any animal she felt like. The trouble was, Harry never knew what animal she would turn into next.
Angela is Charlie's best friend, or best fiend as Charlie accidentally wrote in her essay. But fiend is probably a better word, as it's Angela who puts a spider in Miss Menzies' sandwich, and plasters glue all over Laurence Parker's chair... Angela has a knack of getting Charlie into heaps of trouble but friend or fiend, life is never dull for Charlie when Angela is around!