Deleted Scene: There's 20 minutes of footage left out of the final cut of the movie that is featured on the DVD. For example, there's a scene where Wolfman!Lawrence bursts into a masquerade ball during his London rampage and then proceeds to kill and splatter blood on the guests. It was in the trailers, but didn't make it into the theatrical release.
Development Hell: The movie was planned out and was to be directed by Mark Romanek (of One Hour Photo fame), but he left due to not being able to make changes during the writer's strike at the time. Joe Johnston took over and shot the film in spring/summer of 2008 for a fall 2008 release, but was held back until 2010 due to re-shoots by demand of the studio.
Executive Meddling: The reason the prologue is so short and why a good chunk of character development and establishment are left out is because the execs thought the audience would want more Wolfman and less storytelling. The Director's Cut reinserts many of the removed scenes.