At the beginning of the film, when Roddy is going through his wardrobe, the outfit he forgoes for the Elvis Presley-style rhinestone jumpsuit is a replica of the original Wolverine outfit from the comic books. Wolverine is another role that Hugh Jackman made famous.
Aardman's first fully-CGI feature film. The reason for using computer animation instead of the studio's trademark clay animation was the large amount of scenes involving water, which is nearly impossible to do convincingly in stop motion.
When the stove falls through the floor of Rita's house, a cockroach that was sitting behind it can be seen holding a book. The book is Franz Kafka's novella 'Metamorphosis', the protagonist of which turns into a (non specified) insect, which is often translated as a cockroach. The cockroach appears to be reading a French translation: the title "La métamorphose" is clearly seen, while the Ka- in Kafka is obscured by the insect's 'hand'.
The books on Toad's shelf are "Warts and Peace" by Leo Toadstool, "Unfinished Verse" by Long Tung, "A Brief History of Slime," and his scrapbooks, "The Tragic History of the Great Great Toad, Vol. I," followed by Volumes II through VI.
In the first theatrical trailer, Roddy was not the only pet of the little human girl. There was also a cage with two small yellow gerbils, who seemed to be Roddy's menservants. However, in the final cut of the film, these two characters were removed, probably to advance the story, and make Roddy appear to be a character who is more "alone" than "spoiled". The first trailer also shows the discovery of Sid during the day instead of late at night.
When Roddy and Rita are about to be 'iced' in the fridge, you can see that the controls panel the Toad is using is an early Atari 2600 game console (all the controls on the front). The game plugged into the unit is called "Froggie", a play on the old game "Frogger." When facing the Toad, the label on the back of the unit warns of "no service usable parts inside", and "opening the unit voids the warranty".
The film uses software that was developed for the rabbits floating around the Bun-Vac 6000 in The Curse of the Were-Rabbit (2005). The software reproduces the 'imperfections' found in clay-mation (i.e. dropped frames, thumb-prints, etc.).
In all the movie posters, Roddy is scene wearing a full tuxedo and it was thought that he was going to stay in his tuxedo for the rest of the movie, but he actually wears his white tux shirt and tux pants for the rest of the movie since after being flushed down the toilet his jacket ripped from hitting too many pipes and his bow tie got to wet and soggy from being in the water.