Here's what happens in the commercial:
The commercial begins with a burly, dark-haired and bearded guy in a nondescript brown shirt, brown jacket, and blue jeans sitting in a cluttered garage -- I call him Dave, because he totally reminds me of a friend from Eureka (in Humboldt County), named Dave. Dave from Eureka is of Hispanic descent, but Dave in the commercial I couldn't opine. From the vantage point of the opening frame, there's a motorcycle in front of Dave, and on the side wall, next to a cluttered bookshelf in the corner, is a large wallboard decorated with various knicknacks, including a large orange life preserver and one of those tacky mounted singing fish. After pausing the opening frame to get a closer look, I realized that there is an entire diving suit, helmet and all, slung in a very corpse-like manner atop the piece of furniture (perhaps a refigerator?) adjacent to the corner. Completing the scene, Dave has a McDonald's bag and drink at his side, and sandwich in hand. Indeed, Dave immediately chows down on the sandwich, at which point the shot changes to a closeup of the fish, which turns half its body towards the camera (which is what these wall-mounted singing fish do, after all), and begins singing:
In case you didn't catch that, the wall-fish then repeats the line as Dave just sits there kind of grooving along with the music, even chewing in rhythm to it. He does not appear at all surprised, and his expression could only be described as smug and self-satisfied. We have, in the two quick shots of Dave during this fish-chorus, a point of view from the direction the fish would be looking, and now we can see that Dave is sitting on the end of a workout bench, with a barbell on the equipment's rack behind him, and a cabinet behind that topped by a stereo.
As the fish finishes repeating the chorus, another bearded guy enters the scene -- I call this one Bob, because he looks like a Bob (although he bears a passing resemblence, as well, to Graham Chapman as he appeared in Monty Python's Life of Brian). Bob is tall and looks solid enough, but much less burly than Dave. He has sandy brown hair and an everyman's plaid shirt, and is carrying a fairly sizable drill which he holds up as he enters with the unmistakeable body language which conveys, "hey, here's your big drill I borrowed." To Bob's shock, as he stops right next to the fish and raises the drill a bit to again show that he has it, the wall-mounted fish sets forth on the following exposition of his sad situation:
What if it were you, Hanging up on this wall?
Over the course of this verse, Bob's expression tracks him as he first takes notice of Dave smugly, almost happily watching the fish sing while he eats the sandwich, then a wide-eyed Bob slowly turns to stare in bewilderment at the fish. Bob's eyes turn back to Dave, as if to gauge Dave's response. Dave, never taking his eyes off the singing fish, shrugs. Then we cut to a money shot of the product (which doesn't look appetizing to me at all, though it certainly fills the screen -- a square breaded fish patty topped with a slice of cheese on a typical hamburger bun, with a dollop of sauce getting squeezed out from under the bun. A few more product shots -- the "flakiness" of the fish as the patty (sans bun and toppings) is snapped in half (who eats it like that?); fries; cola being poured over ice; the McDonald's logo, and then a parting shot of that singing fish.
Deconstruction
First, the fish hanging on the wall, although apparently disembowled and otherwise relieved of its bodily substance, is gifted as well with consciousness, sentience, and intelligence sufficient to facilitate communication. However, it appears to be not quite intelligent enough to have a rational grasp of its situation. What is the point of demanding that the "fish" in the sandwich be given back to it? Even if it were returned, it's been processed and cooked. There is no hope for a restoration to a normal state of fishy being. Perhaps the fish is a follower of the belief expressed in certain Native American cultures, that the eating of an animal enables the eater to capture some aspect of the spirit of such animal.... maybe the fish just wants to eat the sandwich in order to get its own spirit back. Maybe the fish is stupid, and just doesn't know that this sandwich can't be it.
This brings up the next point -- an illusion which the ad gamely attempts to create is that the fish in any given filet-of fish sandwich comes from one single fish, rather than being a mongrel of whatever was available that day. Surely Dave isn't sitting there eating a fish sandwich which he personally made from scratch. He's eating one from a McDonald's bag, complete with a McDonald's drink, so unless he happens to work at McDonald's and to have made the sandwich himself (or to have brought the actual fish to a McDonald's and had them make the sandwich from it), it's hard to see how the fish on his wall could have ended up in that particular sandwich (or more exactly, how that particular sandwich could contain any of that fish on the wall).
Dave's reaction to the singing fish is even creepier. No surprise, just a sadistic sort of contentment, the kind which tells you, "yep, I'm devouring your flesh and there ain't nothing you can do about it. Oh, and you taste gooood."
There's a perverse cunnilingus joke yearning to break free from that setup, but I'm not going there.
But this does bring to mind the cartoons of our youth which often featured intelligent, sentient creatures trying to consume other intelligent, sentient creatures. Tom hunting Jerry; Sylvester desiring to eat Tweety; Gargamel hungering for Smurf stew (until he decided to make gold from them instead).
Religion and commerce:
There's even a religious angle here -- the commercial was put together with an eye towards Lent, the mostly-Catholic practice in which the observant give up certain treats, include meat on Fridays, for a 40-day stretch. Fish is still allowed, and due to some ecumenical loophole, this includes crappy fast food fish. A USA Today article relating this information notes, "McDonald's sells about 300 million fish sandwiches annually, 25% during the 40-day Lenten period before Easter Sunday."
The article, by the way, identifies the actors for what its worth, with Ray Conchado (guess he's Hispanic after all!) playing "the guy who shrugs off the singing fish" (Dave), and JR Reed as "the friend surprised to see a fish singing when he walks into the garage" (Bob). Turns out that "Bob" was in Tenacious D in The Pick of Destiny -- well way to go, Bob! They even tell us that the sandwich itself is cod and pollock, but the fish in the commercial is modeled on the pollock because the cod "looked too scary." Okaaaay then....
(I'm told, now, that these sandwiches are "made predominantly from hoki, a gnarly, crazy-eyed fish found in the cold waters off the coast of New Zealand," which McDonald's bought up to 15 million pounds of per year -- until the New Zealand government cut the allowable catch to prevent a population collapse, prompting the add-in of other species.) The article informs us as well that the actors don't speak because they needed to do the commercial in English and Spanish, and apparently only dubbing the fish is the easier way to go. I don't buy it. As a Californian, I know that it's so they don't have to pay the actors scale for speaking parts.
So here we have it -- a self-aware piscene corpse pleading for the restoration of its flesh, and an unconcerned possible eater-of-sentient-beings taking joy in the anguish of the beast. And that is supposed to compel you to find this product appetizing. Maybe that's the real message which McDonald's is trying to send here, "come taste the forbidden fruit of the flesh of a thinking creature," the closest we can get to true fast-food cannibalism.
There is by the way a somewhat satisfactory alternative explanation for the events in the commercial, which is that this is a practical joke which Dave is springing on Bob -- that is, Dave set up the electronic talking fish to be triggered by its motion sensor to sing that particular message whenever someone walked by, and then sat there with a filet of fish sandwich until Bob came along. Thus, Dave would freak Bob out by creating the appearance of a self-aware and justifiably displeased wall-mounted fish. Which would as well explain Dave's smug mirth at Bob's obvious discombobulation in the presence of the spectacle. But a close review of the ad shows no one at all around the fish to trigger its singing, nothing to explain that effect except Dave's sandwich-eating act. Maybe Dave just saw Bob coming and had a way to trigger the fish so that it would reach the critical verse when Bob get to that closest point to it.