Baggy Trousers was the original title for The Inbetweeners and name of the shows pilot which was produced in 2006 under the direction of James Bobin. All that is known about Baggy Trousers comes from a 1:17 video uploaded to Vimeo in 2013 by Keith Watts who worked on the pilots artwork, and later from actors James Buckley and Darcy Thomas, after Buckley found the video through this page.
The pilot features five named characters played by different actors from the main series, but featuring main series cast member James Buckley.
William - Matt Green
Neil - James Buckley
Lee - Darcy Thomas
Carli D'Amato - Laura Aikman
Alex Macqueen, who played Kevin Sutherland in the main series appeared in the pilot in an unidentified role.
James Buckley, who played Jay Cartwright in the main series appeared in the pilot as Neil, which he revealed in a tweet after seeing this page. This brought attention to the Vimeo video, which was removed by channel 4 or Watts, and has been lost. One twitter user enquired whether the actor playing Will was comedian Matt Green, who seemed to confirm it was him. A week later, Digital Spy published an article about Darcy Thomas who played Lee, who described his character as a 'similar kind of character to Jay - champion blagger'. It is unknown whether the Baggy Trousers pilot has been archived and still exists, but hasn't yet surfaced.
The pilot appears to have the same script to Bunk Off as Simon is shown spraying 'I love Carli D'Amato' on her drive. William is also shown wearing a suit presumably to buy alcohol like in Bunk Off.
Laura Aikman, who played Carli, appeared briefly in the main series Bunk Off when Will talks about staring at girls in the park. It is likely this was re-used footage from the pilot.
The name Baggy Trousers likely comes from the sagging fashion culture.
There is no known character called Jay in the pilot and he was preceded by a similar black character called Lee. Why Lee's name and ethnicity were changed is not known.