Thomas, You're the Leader, sometimes called Roll Call Rap, is a song from The Great Discovery.
The song is based on Engine Roll Call, but with additional verses about the Skarloey Railway engines, the Pack and the remainder of the vehicles. A second altered music video was later made using footage from the thirteenth series. The Skarloey Railway engines, the Pack, Stanley and various other characters were cut out though, as they did not appear in the CGI Series at the time.