Ratatouille — Easter Eggs & Hidden Details

Behind Remy, while Linguini talks to him, sit two tins labelled Nemo brand caviar. Caviar is fish eggs. The joke is that Pixar took the most beloved fish character it had ever produced — the one whose film was built entirely around a father's terror of losing his son — and put his name on a delicacy made of unhatched young. It remains one of the darkest cross-references the studio has ever shipped, and it is on screen for a couple of seconds with no comment at all.

Git, the big scarred rat in Django's clan, is a former laboratory animal, and the tag clipped to his ear reads A113. Pixar's warmest in-joke — the CalArts classroom where Brad Bird, John Lasseter and Andrew Stanton studied — is here recast as the identifier stamped on a test subject. The film plants a second one too: A113 appears on a train in the background of the film Linguini watches on television.

Pixar's most-travelled vehicle makes its Paris appearance on a bridge over the Seine, passing through frame while Skinner chases Remy across the city. Getting the truck into a period-flavoured French film without breaking the world is exactly the kind of constraint the gag thrives on — the crew has since had to sneak it into medieval Scotland and prehistoric Earth.

One of the street performers in Paris is Bomb Voyage, the mime supervillain Mr. Incredible fights in the prologue of The Incredibles. Both films are Brad Bird's, and he moved the character across without a single line of acknowledgement. Fans have argued for years over whether this is the same criminal gone straight, a cameo with no continuity attached, or a director quietly reusing a design he liked — Bird has been happy to leave it alone.

During the frantic business of hiding a rat under his clothes, Linguini's underwear turns out to carry the Incredibles insignia. It is a throwaway sight gag, but it is also the second Brad Bird self-reference in the same film, which makes the pattern deliberate rather than incidental — Bird was quietly stitching his two Pixar features together in the background.

The dog whose silhouette lunges and barks at Remy during his flight through Paris is Dug, the golden retriever from Up — which would not open until 2009. Pixar's habit of seeding the next film into the current one is at its subtlest here: Dug appears as a shadow rather than a character, so there is nothing to recognise until the film he belongs to exists.

The critic's study is not decorated like a study. The room is built as a coffin — narrow, tapering, lidded — and the typewriter he writes his executions on is shaped to read as a skull. Nothing in the dialogue points at it. It is pure production design doing characterisation: the man who can kill a restaurant with a paragraph is drawn working inside his own funeral furniture, which makes his eventual review land as a resurrection rather than a change of mind.

Gusteau's is invented; its room is not. The production drew heavily on La Tour d'Argent, the historic restaurant that sits on the bank of the Seine looking across at Notre-Dame and the Île Saint-Louis, and reproduced specific fittings — the lamps and the cheese trolley among them. It gives the film's fantasy of haute cuisine a real address, and it is why the dining-room scenes feel researched rather than imagined.

While Remy is down in the Paris sewers, the soundtrack carries a barely audible "Dead men tell no tales" — the line that greets riders at Disneyland's Pirates of the Caribbean. Audio easter eggs are rarer than visual ones because they survive no freeze-frame; you either catch this on a good system or you never know it is there.

After the loop groups and the production babies, the very last thing in Ratatouille is a quality-assurance stamp: "100% Genuine Animation! No motion capture or any other performance shortcuts were used in the production of this film." — beside a winking 1950s ad-man giving a thumbs up. Read in 2007, with performance-capture features arriving annually and industry arguments raging about whether they counted as animation, this was not a whimsical sign-off. It was Brad Bird planting a flag on behalf of hand-keyframed animation, in the smallest type in the movie.