It was when the level designers/programmers/I forget who found that after creating levels there was plenty of space left to add in extra things, they decided to put in some 'secrets', but wouldn't say what they are, hence we don't know exactly what they're talking about, although some interesting things have been found in the game, in film and in-game. These include:
- Disected Elums in the Vykker Suites
- A mention of Molluck in the Scrab Retreat
- Hint Flies at the start of the Mudokon Pens
- SoulStorm Brew in the Poop Chute
- The Slig marching movie in the Boiler Room
- At least one Magnum Slig near the beginning of the FlubCo Scrub Pens
- A couple of chemistry sets behind bars in Fuzzle Testing
- The giant skeletons in the Paramite Run and Scrab Retreat
- Slig lockers and the Labour Eggs sign at the end of the Loading Bay level
There's tonnes of little things to notice, though, just do some exploring. What was originally in the game and what the creators added is not known, but it's fun looking about. No hidden movies, though - at least it's highly unlikely.