Commentaries and special features can vary depending on the DVD region you are watching so it is important to include that information in your reference.
Format: in text citation
Producers offer a look behind the scenes that actors and directors often see differently (Title, Year).
Format: reference
Title of feature (Year) Title [Format]. Place of production: Production company. Region.
Example: in text citation
Producers offer a look behind the scenes that actors and directors often see differently (Convention panel with producers, 2011).
Example: reference
Convention panel with producers (2011) The Walking Dead, Season 1 [DVD]. [s.l.]: Entertainment One UK Limited. Region 2.