The first three minutes of the scene with The Marauders at the bar was completely ad libbed, with a story that was thought up on the day of shooting. This was done on purpose due to the chemistry seen between the four actors during rehearsals.
The subtle whispering voices during Voldemort's reveal are voices speaking in Parsletongue. Since there is no official language for it, the filmmakers wrote several phrases and sentences warning Snape away from Voldemort in various degrees. The voice actor then spoke the words backwards.
The paintings in the background all move. They include the actors from the previous fan film "The Greater Good" who played Ariana Dumbledore and Aberforth Dumbledore, the four founders of Hogwarts, two seamstresses working on a dress, a Quidditch player who was played by Alex Benepe - the founder of American International Quidditch Association, and two cameos by fans who were contest winners.