Several of the women who turn out to see Bilbo and the Dwarves leave Lake Town for Erebor are actually tall male crew members, who were dressed up as women to get the proper scale of humans versus dwarves and Bilbo for the shot.
The only time Legolas blinks is when he realizes he has been wounded and when Thranduil beheads the orc he is interrogating. This is in keeping with the character, as the only time Legolas blinks in The Lord of the Rings trilogy is when he is strongly surprised.
The Mirkwood scenes required nearly all color to be drained from the footage, in order to make the forest appear "sick". As a result, objects that needed to retain their color, such as certain mushrooms and lichens, had to be painted in neon colors to be noticeable at all in the final movie. Sir Peter Jackson remarked that the set looked like it was painted in 1967. The actors also had to have their faces painted unusually red in order to retain color.
While the cast was shooting the barrel escape scenes in the specially-constructed indoor "rapids" tank, several of them stated that they had to relieve themselves in the water, since they had to stay in the tank for so long without so much as a lunch break. When Martin Freeman found out he was furious, since Bilbo spends all of his time during that scene directly in the water, and had been swallowing a great deal of it.
The sudden scars on Thranduil's face are a creation of the movie adaptation. However, his scars may reflect a little-emphasized facet of J.R.R. Tolkien's lore: Elves' "Fëa" (a metaphysical concept analogous translatable as "soul") occasionally influences the "Hröa" (the fleshly, physical body), particularly under moments of extreme stress. This can manifest as extreme physical changes that reflect the mind's state, in this case deep war scars. This is in accordance to J.R.R. Tolkien's texts and books, the last battle where Thranduil fought, was the Last Alliance at the end of the Second Age (about three thousand years earlier), where Sauron was defeated.
Alan Lee: The conceptual designer appears as one of the musicians when some of the Dwarves, and Bilbo, leave Laketown. He also appeared as one of the nine Kings of Men in the introductory scenes of Il Signore degli Anelli - La compagnia dell'Anello (2001).
Royd Tolkien: The great-grandson of J.R.R. Tolkien is in the Extended Edition in a flashback as one of the Captains of the Gondorian Rangers burying the body of the Witch-king of Angmar. This was an homage to Royd's cameo in Il Signore degli Anelli - Il ritorno del re (2003) as a Gondorian Ranger at Osgiliath.
Stephen Colbert: As the eyepatch-wearing Lake Town spy who knocks on the door with the walking stick. Colbert, a longtime Tolkien fan and expert, had brought his wife and two of his sons to the shoot. When his scene was completed, Peter Jackson personally presented Colbert with a replica of the sword Sting.
Peter Jackson: At the beginning of the movie, as the camera sweeps through the town of Bree, he walks out of the pub looking drunk and eats a carrot. He had a similar cameo in Il Signore degli Anelli - La compagnia dell'Anello (2001). Jackson also filmed another cameo for this movie. He played another spy in Lake Town, a man who'd hide in a basket and signal his comrades with wild bird calls. The scene was adamantly vetoed by his co-producer and co-writer, Philippa Boyens, and was never used.