With the brilliant animated films “Iron Giant” and “The Incredibles” already under his belt, writer-director Brad Bird comes to “Ratatouille” with great expectations heaped upon him. Adding to the pressure is the fact that many people viewed “Cars,” Pixar’s last effort, as representing a slight decline in quality after such acclaimed efforts as “Finding Nemo,” “Monsters Inc.,” and Bird’s own “Incredibles.”

“Cars” must have been an anomaly, then, because “Ratatouille” is as almost as funny, joyful, and heartfelt as anything that Pixar’s merry band of genius-nerds has ever done. We’re at the point now where you can just say, “It’s a Pixar movie,” and that sums it up.

Our hero is Remy (voice of Patton Oswalt), a rat of undetermined age who lives with his colony in the French countryside near Paris. He is unique among rats because he has a refined palate. While everyone else sees mere garbage and feasts upon it, he sees the individual ingredients and is appalled by them. Like so many of his Disney brethren before him, he yearns for something more than this humdrum existence! He longs to dine on tasty foods exquisitely prepared. He wishes he were someplace where his gourmet sensibilities were appreciated, not mocked, as they are by his father (Brian Dennehy) and simple-minded brother (Peter Sohn). (Another thing Remy shares in common with his Disney brethren is that he does not seem to have a mother.)

An emergency forces the rats out of their dwelling into the sewers, where Remy is separated from the group and winds up, as luck would have it, in the crawl space at Gusteau’s, the finest restaurant in all of France! The late Chef Gusteau (Brad Garrett) was famous for his “Anyone can cook!” philosophy. Remy has seen reruns of his TV show, courtesy of the old woman whose attic the rats used to live in, who frequently fell asleep in front of the TV. Now the spirit of Gusteau appears to Remy as a guide, a conscience, and a figment of his imagination, encouraging him to follow his dreams.

From Remy’s vantage point in the ceiling, we see the kitchen at Gusteau’s. The new chef is Skinner (Ian Holm), a short, angry little man who has sold out Gusteau’s name to merchandisers, with microwaveable products like Gusteau’s BBQ Dip ‘n Ribs now in your grocer’s freezer. The restaurant’s five-star rating has dwindled to three, due in part to negative reviews from the great food critic Anton Ego (Peter O’Toole), an austere, humorless man who takes no pleasure in anything. The restaurant is surviving, but just barely.

Skinner is obligated to hire a clean-up boy named Linguini (Lou Romano), an awkward young fellow whose mother was a friend of Gusteau’s back in the day. Linguini doesn’t want to become a chef, particularly, recognizing he has no talent for the culinary arts; he can barely take out the trash without screwing it up.

Through a series of hilarious and strangely logical events (if you can accept that a rat understands human speech and knows how to cook), Remy and Linguini become partners. Remy can cook, but he’s a rat. Linguini is in the kitchen and has the opportunity to make something of himself, but he has no skills. Together, they can do it. Or as Linguini sums it up to his new rat friend, “You know how to cook, and I know how to appear human!”

Soon Linguini is the toast of the town, elevating Gusteau’s back to its original place of prominence. He prepares his masterpieces by putting Remy under his chef’s hat, where the rodent pulls Linguini’s hair like a rider controlling a horse’s reins, guiding him to the right ingredients and preparations. No one can know his secret — they would think he was crazy if he told them a rat was his mentor — and Skinner becomes increasingly jealous and suspicious of this gawky new prodigy.

I am delighted by every aspect of the film, from Michael Giacchino’s perfectly breezy score, to the whimsically bizarre storyline (how does anyone even think of something like this?), to the way that crazy story is brought to life reasonably and intelligently by Bird’s nuanced script. There is a surprising complexity to the film, with multiple relationships being juggled all at once. There’s Remy’s connection to his dad and brother, his conflicting desire to be a gourmet chef, Linguini’s crush on fellow cook Colette (Janeane Garofalo), Remy’s association with Colette (they’re both competing for attention from Linguini), Skinner’s paranoia that there’s a rat living in the kitchen. The rightful ownership of the Gusteau brand name comes into play, as does Remy’s desire to stop being a “thief” (that’s what rats are, you know). And somehow, Anton Ego figures into the whole thing.

The comparative ease with which computer-animated films can now be made has led to a rash of bad ones: “Hoodwinked,” “Happily N’Ever After,” “Everyone’s Hero,” “Madagascar,” and so forth. Enduring those movies’ gracelessness makes you appreciate it all the more when someone comes along and does it right. “Ratatouille” is packed with beautiful images of Paris, drawn to look quaint and old-style, though the film is apparently set in the present. There are imaginative camera angles and movement, and a stunning attention to detail. The characters move and emote with fluidity, not stiffly, the way some films would have it. Even the way Skinner pours a glass of wine, with that slight rotation of the bottle at the end of the pour, is perfectly rendered. Pixar has, once again, raised the bar on the technical side of making an animated film.

The non-technical elements don’t lack, either, though it’s fair to say it’s not the most emotionally overwhelming thing Pixar has done. It doesn’t pack the punch of “Toy Story 2” or “Finding Nemo,” for example; the characters, while engaging and sympathetic, don’t connect with the audience at quite that level. That’s more an observation than a complaint, though. There really isn’t much at all that I would change about this visual, imaginative feast.

A- (1 hr., 51 min.; G, with scenes of mild peril and some mild grown-up themes; should have been PG.)