The only acceptable alias for a Director to use for himself, according to the Director's Guild of America (DGA).
Alan Smithee, as his node will tell you, has a history of directing awful films since the 1950s. If a film's management was suspected of making excessive edits or changes that endangered a film's artistic integrity, the director could appeal to the DGA for permission to strike his name from the credits and insert Alan Smithee's in its place. Alan Smithee films tend to bomb at the box office or go straight to video, so the poor director is spared the agony of being associated with a disastrous project.
The film An Alan Smithee Film: Burn Hollywood Burn was released in 1997. This film, meant to be a mockumentary on the filmmaking process, went horribly wrong itself and ended up being directed by Alan Smithee. It grossed about $45,000 at the US box office and came nowhere close to recouping its $10,000,000 budget. However, it became more notable for letting the cat out of the bag about Alan Smithee. The DGA decided to phase out the name after the film's debut. The last Alan Smithee film premiered in 1999.
The DGA now approves Thomas Lee as the only acceptable pseudonym for a director. The process for using Lee's name has the same qualifications as with Alan Smithee. The first and (as of August 6, 2003) only film directed by Thomas Lee is 2000's Supernova, which IMDb still credits primarily to its real director Walter Hill.
Thomas Lee sounds like an innocent-enough name, but one has to wonder: did the DGA ever hear of a certain drummer and public figure named Tommy Lee? Seeing that Lee is a fairly common surname in America, there will be great irony when a real Thomas Lee has to change his name in order to be taken seriously as a director in Hollywood.