- Actor-Shared Background: Half the cast of Blue Heelers would wind up in the series at some point or another, though most of the characters would not meet each other as they would have in the other show with PJ/Mario and Graham (Gerard Kennedy and the guest roles he played) being the only notable exception.
- All-Star Cast: Channel Nine were serious about the project and drew on some of Australia's best and most beloved actors, picking from those currently and formally on heavyweight shows. See Hey, It's That Guy! below.
- Banned in Victoria: The first season was banned in Victoria by way of a court order, as the trials of several people involved in the events depicted were underway at the time and there was an interest in preventing the jury being influenced and prejudiced by watching the show. Judge King went so far as to enjoy the attention for banning any media story based around the gangland killings. However, freak weather conditions in Tasmania sent the signal for episode 5 to parts of Victoria. Additionally, the ban was publicised quite a bit by media outlets, sparking even more interest in the show.
- Enforced Method Acting: Actor Simon Westaway played suspected gang associate Mick Gatto, and when the two met one of Gatto's associates noticed Westaway copied what he did, which hand he ate and drank with. Despite Gatto's concern of a former police officer playing him he saw that the actor was fair dinkum about the role.
- Hey, It's That Guy!: Underbelly was a who's who of top Australian actors: Vince Colosimo, Gerard Kennedy, Frankie J Holden, Caroline Craig, Martin Sacks, Damian Walsh-Howling, Roy Billing, Matt Passmore, John Wood, Jane Alisop, Ditch Davey, Saskia Burmeister, Peter Phelps...
- No Export for You: No plans yet have been made for the fourth season to air in the US as of yet, as Audience Network has opted to skip it in favor of going straight to season five.
- Name's the Same: Here's an odd one given they're both real people: Ann Marie. Bob Trimbolie's restaurant owner turned lover or co host of the 90's Aggro (a Australian puppet) Cartoon Connection?