Matt Groening came up with the idea for The Simpsons, but that doesn't mean all his ideas are winners. Like, for instance, Marge Simpson being an anthropomorphic rabbit disguised as a human.
*record scratch* Say wha--?!? Here's Daria Paris, who was the assistant to former executive producer Sam Simon, as quoted in John Ortved's The Simpsons: An Uncensored, Unauthorized History:
There were times in the room when Matt would come up with the stupidest ideas. And he had this one: we were going to do an episode where Marge finally lets her hair down, and Matt's idea was that once she let it down the audience finds out she has rabbit ears, which was ridiculous. And Sam said no.
And here's what Groening had to say about it on the audio commentary for Selma's Choice, when writer David M. Stern brings it up and puts him on the spot:
That was the original - back in the - my plan, back in the very beginning, that she was actually a Life in Hell rabbit from my comic strip... but then it just seemed like a... I just said "oh, forget it, there's no ears under there."
"Ridiculous" is putting it lightly. Here's how I'd like to imagine that transpired: the writers and producers are seated around a giant table in a Dr. Strangelove-like Situation Room. Matt Groening causally brings up his idea that Marge Simpson - loving wife, devoted mother, future Playboy centerfold - is a rabbit in disguise, a secret that would be revealed in the final episode. A long, awkward silence ensues, as the writers sit in stunned disbelief at the utter insanity their boss just uttered. Suddenly, Sam Simon starts yelling at Groening about what a stupid idea that is. After a big back-and-forth about the plausibility of the whole concept, Simon finally puts his foot down, and Groening shame-facedly retreats to his office, to console himself with money. And thus we were all spared from the horror of Marge's closet rabbitness being An Actual Thing.
...OR WERE WE?!?!
As it turns out, Groening did get his his way, after all - at least in The Simpsons Arcade Game. Here's some sprites taken from the game, ripped by someone named Random Talking Bush:
As you can see, Marge clearly has rabbit ears. And they're right there in the game, just waiting for you to notice them.
You might still find this game in your local arcade, or you can play it on an emulator or something, and you can see Marge Simpson's Rabbit Ears for yourself. (Also of note: some of Groening's Life in Hell rabbit characters appear in the game - Binky and his one-eared son Bongo make glorified cameos. Apparently Groening saw Life in Hell and The Simpsons as being part of the same universe. And, had he gotten his way, this aspect was eventually going to become canonized as part of the series. Oh, what could've been.)
At the time, Random Talking Bush attributed the weirdness to game publisher Konami being a bunch of weirdos with a "strange sense of humour." But now we know it came directly from the top. [The Spriters Resource]