Lisa Simpson is known to be wiser than her years. Her genius lines eliminate the show. She serves gems, like, "Mom, romance is dead. It was acquired by Hallmark and Disney in a hostile takeover, homogenized, and sold off piece by piece (Season 6: Another Simpsons Clip Show)," or "Well, I'm going to be a famous jazz musician. I've got it all figured out. I'll be unappreciated in my own country, but my gutsy blues stylings will electrify the French. I'll avoid the horrors of drug abuse, but I do plan to have several torrid love affairs, and I may or may not die young. I haven't decided (Season 3: Separate Vocations)."

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But even the most enlightened minds belong to humans and can blurt out some really dumb things. And because of her wisdom and genius, people often forget, that Lisa is just a child, and children can often say dumb things. As Bart sang, "Lisa is so stupid. So very, very stupid. So dumb and stupid, and smelly, too."

10 "Solitude Never Hurt Anyone"

The Simpsons Lisa Lying on Her Bed

During season 8's episode, "The Secret War of Lisa Simpson," Lisa utters the line, "Solitude never hurt anyone." Most people know this to be false by experience, but once or twice, everyone has considered a life in eternal solitude. For a child like Lisa, it might be a tempting alternative, but she will, too, realize that it's not that easy after all.

9 When Babysitting Went South

The Simpsons Lisa, Maggie and Injured Bart

Responsible or not, parents often let siblings be each other's babysitters when they go out. It's a good way to save money, and if someone has a wise and smart daughter like Lisa, it could even be a smart decision. But once something goes south, Lisa made the wrong decision in season 8's, "My Sister, My Sitter," by not calling the ambulance or her parents to help her brother after a serious accident.

While for an adult this is without a question a dumb decision, Lisa is still just a child, who sometimes can't weigh the rights and wrongs when panicking.

8 "According To Eternity Magazine, You Can Lose Weight Through Subliminal Learning"

The Simpsons Lisa Reading Eternity Magazine

Magazines named like "Eternity Magazine" have the habit of spreading myths such as, "[...] you can lose weight through subliminal learning," as stated by Lisa in season 3's "Bart's Friend Falls In Love." People who buy into these so-called scientific facts, for even a second, are more often than not, considered dumb. At least for a time, Lisa did too.

7 When She Ruined Bart's Chance To Be Better

The Simpsons Lisa Sabotaging Bart

Despite having all the smarts and wisdom, Lisa could be very mean, vindictive, and jealous. These brought the worst out of her, pushing her practical thinking aside. In one episode, Bart, first with alternative motives, joined a feminist group. After getting to know the group and the cause, Bart decided he wants to do good and started working with them.

Lisa, instead of being proud of his brother's progression, out of jealousy decides to stop the madness and make Bart go back to his old ways. She tells him that he can't do anything for this cause, and she should be working with this group instead.

6 When She Gave Bart Coma-Nightmares

The Simpsons Lisa with Bart in a Coma

Siblings can be unreasonably mean from time to time, and they can often cross a line. After Bart is struck by lightning in season 29's, "Flanders' Ladder," he falls into a coma.

Lisa starts to provoke nightmares, which makes Bart's experience in the hospital worse and ultimately threatens his life in the real world. This could seem like typical sibling meanness, but Lisa, being a smart and capable girl, should know that this decision is dumb. It seems Bart is the best person to cloud Lisa's judgment.

5 When She Sabotaged Bart's Career

The Simpsons Bart's Career in E-Sports

Not being able to share her spotlight, Lisa once again turns someone else's chance into being an opportunity for her. While Bart has a chance to win a substantial amount of money in an E-Sports tournament in season 30's "E My Sports," Lisa makes it her mission to take her family to a monastery, ultimately resulting in Homer destroying Bart's chance to win. Although Lisa didn't intervene herself, viewers can recognize her intent on sabotaging her brother.

4 When She Stole The Teachers' Edition Books

The Simpsons Lisa and Bart Discovered Stealing Books

Lisa rarely lost her temper, but when she did, she went big. After a series of blows to her self-esteem in season 3's "Separate Vocations," she decides to steal all the Teachers' Edition books in the school.

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When Bart finds this out he turns himself in and took the blame, saving Lisa from staining her future prospects. If it wasn't for Bart, she could've been expelled for her wrongdoings.

3 When She Ruined Homer's Barbecue

The Simpsons Lisa Steals the Barbecue Pig

Lisa is a pivotal character in the series as deep, educational, and political themes are written through her. One of those topics involves Lisa becoming a vegetarian in season 7's "Lisa The Vegetarian." This decision is a big part of her character.

But acting again like an eight-year-old, which she is, Lisa sabotages Homer's barbecue by stealing the pig. Understandably, she feels lonely as almost no one understands her, but it's still not a good reason to push her beliefs onto others.

2 Dropping Bart From Her Team

The Simpsons Lisa Studying to Make Perfect Baseball Team

Lisa's worst quality is the way she impulsively acts without thinking about the consequences. Being the smartest and wisest of the family, viewers would think she's well calculated, but her childlike nature clouds her mature conscience sometimes.

In season 22's "MoneyBart," Bart and Lisa team up to statistically calculate the best baseball team. When it seems as though Bart is a better asset to the team than Lisa, he starts to ignore her advice, and as a result, Lisa cuts him off the team. She ultimately realizes her mistake, but this type of error seems to be a pattern in her life.

1 When She Almost Killed Clara

The Simpsons Lisa Sending Clara on Dangerous Path

Season 14: Dude, Where's My Ranch?

Lisa's jealousy rears its ugly head every now and then, but the behavior she exhibits in season 14's "Dude, Where's My Ranch," takes the cake. When on a ranch, she falls in love with a boy and overhears him talking to a girl named Clara.

Without giving it much thought, Lisa sends Clara on a highly dangerous path when she asks for directions. Thankfully, she survives, but ultimately, Lisa finds out that Clara is the boy's sister. This is the dumbest Lisa's been in the series.

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