Casey Jones, the voice actor that plays Belzar, appears twice in the film onscreen. He plays one of the three muggers that Dennis fights early in the film and a street savage covered in war paint that Dennis also fights nearer the end.
In an early scene when the character Simon is lying on his bed, he looks at his phone and comments on an email he's received about a gig called "Live 10 Whelan's" that he might go to. This moment was unscripted and was actually just footage of Conor O'Toole out of character and looking at his phone while the shot was being prepared.
Dave Duffy and Colm Kearns appear in discussion during a news broadcast in the film. Kearns starred in the lead role of Séamus Hanly's previous film 'BenD' in which Duffy played the villain.
The man being attacked by three muggers, that Dennis saves, is played by Diarmuid O'Brien, the film's assistant director and head of special effects.