1. The first and last house named in the series was Slytherin.

2. J.K.R. has stated that no death rather besides Snape could produce a Patronus, or at least never try. Snape's Patronus takes the form of a doe, the same as Lily Potter.

3. After Fred's death, George Weasley will never be able to produce a Patronus, because all his happy memories involved his twin.