The Beverly Hillbillies: Elly May Clampett's cooking is nigh inedible. Her biscuits and donuts are hard as a rock and just as heavy. One episode sees her make a meatloaf in the shape of a giant meatball. Said meatloaf bounces like a basketball.
The Hong Kong game show Beautiful Cooking is built completely on this trope. Its rating scale goes from 10, which is "Looks and tastes edible" to a -10, which is "I vomited more than once". There are some girls who can't cook well for the first event or the latter while some are just completely hopeless. In one case, one of the guests got food poisoning and had to be treated to the season finale dinner to compensate for the suffering he went through.
Worst Cooks in America is a reality cooking show featuring people who're obviously terrible cooks, and the people who compete were nominated by friends, relatives, spouses or significant others, or even themselves, and many of the people have even accidentally given others food poisoning through what they've cooked. The point of the show is to teach some Lethal Chefs to become good enough cooks to actually make a restaurant-quality meal for a trio of food-expert judges.
One Sweet Genius contestant used raw eggs in a dish. Chef Ron nearly threw him out of the kitchen on the spot.
My Parents Are Aliens. Virtually everything cooked by Sophie Johnson uses rather... nonstandard ingredients. Like sausage cake, or chicken nuggets — complete with bones, feathers and "fresh" chemical additives.
Neelix is legendarily bad, often cooking meals that are disgusting to the human palate. When he sticks to the basics or uses a recipe then things turn out fine, but when he tries to show off his exotic skills (anything with Talaxian spices is a warning bell) the wheels come off. In one episode, he nearly caused ship-wide failure by infecting the ship's neural gel packs with bacteria from curdling cheese.
Captain Janeway manages to ruin food that comes from the replicator!
The series finale tells us that the Bolian crewman Chell wants to take Neelix's place as the chef. He presents some...interesting dishes in his proposal to the captain, including "Red Alert Chili" and "Chicken Warp Cordon Blu" (say it aloud). Thankfully, the ship made it home before his skills could be put to the test.
In one episode of Star Trek: The Next Generation, Riker invites a few of the other officers over to show off his experimental cooking (some sort of alien omelette). Most of them are clearly attempting to conceal their distaste, while Worf eagerly scarfs up his portion. In a later episode, Riker is shown apparently enjoying Klingon dishes.
Quark was apparently a Lethal Chef, necessitating certain defensive measures.
Quark: This is my disruptor pistol. The one I used to carry in the old days, when I was serving on that Ferengi freighter. Odo: I thought you were the ship's cook. Quark: That's right, and every member of that crew thought he was a food critic.
At one point late in the last season, Sisko walks in on his now-wife Kasidy Yates to find she's tried to cook dinner for him and failed miserably. (This is a setting where most food is replicated, remember.) He spends a few moments mourning the loss of the hot peppers he'd spent several weeks growing himself.
On The Munsters, Grandpa's lasagna has been known to stink up the entire house.
Rimmer only attempted to cook once, but it was enough for both his living crewmates to require stomach-pumps.
Lister: Rimmer, real dumplings, proper dumplings, when they're properly cooked to perfection, real, proper dumplings should not bounce!
Dave Lister's own attempts at cooking aren't much better. During the earliest episodes, Lister tries to qualify to become an officer, so that he would outrank Rimmer. Lister goes for the Chef exam (because even the ship's cook outranked Rimmer), but fails horribly. One reason might be that Lister, being a total slob, understands recipes not as guidelines but merely as suggestions. Another reason is that Lister's overly fond of curries, and he claims that after years on a curry diet his tastebuds have suffered. Lister does try to cook from time to time, but his attempts always suffer from some fatal flaw, such as stuffing sausages with curry powder. His "Shami Kebabs Diablo" (take exactly one teaspoon out of a full tin of chilli powder. Put the rest into the mixture) put his friend Peterson in sickbay for a week. Or cooking a three-course meal which looks fine at first glance, but due to lack of proper plates and eating utensils is served on (and in) items that Lister raided from sickbay. All properly washed and sterilized beforehand, of course! Still, it puts the Cat off eating.
Cat: This isn't a meal, this is an autopsy!
While Lister's fried egg chutney sandwich is quite deadly in its own right (Rimmer describes its taste as "melting his teeth"), the fact that the recipe was obtained from a biological warfare book (he uses it as a Hideous Hangover Cure) lampshades this aspect and Rimmer finds the deadliness of it to be its crowning aspect, putting this recipe in the delicious but deadly territory.
Lister: You have to eat it quickly or the bread will melt.
Oddly enough, when he was preparing for the exam Lister did make a beautiful looking cake. He might have passed the test if he hadn't been trying to make roast beef instead. In the next series, Lister makes another pleasant looking cake to celebrate Rimmer's "Deathday".
Another time Lister fed a T. rex a giant bowl of "cow vindaloo", it took two tastes of it then ran for a drink. The other results were unfit to show on television. Though in that case, it was more or less what he was trying to do as earlier it had eaten a time-manipulation device and they needed it back.
In the second episode of Jonas, the boys order pizza from a place that makes very disgusting pizzas, simply because they have a crush on the delivery girl.
Baldrick in Blackadder. Naturally, he is also the only chef from series 3 onwards. In series 4 he has the excuse of limited resources, but there are some things that an excuse just can't cover:
Blackadder: There are amoeba on Saturn that can boil a better egg than you. Your filets mignon in sauce Bearnaise look like dog turds in glue.
Baldrick: That's because they are.
Blackadder: Your plum duff tastes like it's a mole hill decorated with rabbit droppings...
Baldrick: I thought you wouldn't notice.
Blackadder: And your cream custard has the texture of cat's vomit.
Baldrick: Again, it's...
Lisa Douglas from Green Acres. Her infamous "hotscakes" have the consistency of bricks. Mr. Douglas was terrified when his neighbor, Mr. Ziffel, asks Lisa for a shopping bag full of her pancakes. Mr. Douglas, very worried, asks him if he's going to eat them. Mr. Douglas calms down when he finds out Mr. Ziffel only wants them to reshingle the roof of his barn.
Rachel tries to prepare a traditional English trifle, but the pages of the recipe book get stuck together and she ends up making half a Shepherd's Pie: a trifle containing jam, custard, ladyfingers, and beef sautéed with peas and onions. Ross says that "It Tastes Like Feet", but that doesn't stop Joey: "Custard? Good. Jam? Good. Meat? GOOD".
Monica reviews a restaurant and calls the food inedible. "None of my friends could eat it, and one of them eats books!" (Joey, of course.)
In "The One with the Bullies", Joey packs an olive loaf and ham spread sandwich for the roadtrip to meet Phoebe's biological father and is forced to throw it out of the car to distract Phoebe's stepmother's dog. According to Rachel, this tactic is less than successful: "(that dog) will lick itself but it will not touch your sandwich, what does that tell you?"
In general, Monica is an excellent cook, but in the seventh season, she tried to reverse engineer Phoebe's grandmother's cookie recipe and did a lot of baking. Most were quite good, except for batch 16, which made Ross throw up.
The point of the British Reality ShowKitchen Criminals is to get horrendous cooks around England and have world class chefs teach them how to cook fine cuisine for a food critic. Some of the contestants when they first started tried to serve shrimp raw or fry an apple core.
A running gag in My Family is that Susan, the mother of the titular family, is the worst cook in the world. One Christmas episode featured not only chocolate raisin turkey with caramel (due to pages of the cookbook being stuck together) but also this exchange.
Ben: Before that was the year of the turkey. Susan: OK, so it needed to be in for a bit longer. Ben: Susan, it was still alive.
Lucy from I Love Lucy is bad, but she's demonstrably better than both Ricky and Fred, as shown in the episode where the men undertake the women's typical responsibility and vice versa. Ricky ends up flooding the whole apartment with rice when he assumes the proper portion is one pound per person. And Fred, in charge of the dessert, decided to save time, by baking all seven layers of the cake, including the frosting, into a large flat pancake shaped... thing.
A skit on All That is called The Filthy Chef which is a parody of The Naked Chef.
Joxer of Xena: Warrior Princess. In one episode, Xena and Gabrielle are incapacitated (by skin fungus and head lice) and it falls to Joxer to defeat the entire invading army — by cooking for them. He's actually successful. Too bad our heroines discover his "skill" by first falling victim to it themselves....
Chelsea in Raven's Home. In the pilot episode, she accidentally set a fire while trying to cook twice and Levi even ordered pizza in case she decided to cook again. In the third episode, the Cranky Landlord accused her of trying to poison him with the coffee she made.
Becky on Full House has this reputation, one episode even has a B-plot with her and Michelle learning to cook together.
Becky: Remember that sausage and lima bean casserole I made? I called it my Sunday Surprise.
Danny: We called it our Monday Surprise.
Jesse: I was still getting surprised on Tuesday.
Thelma from Amen was a notoriously bad cook. In one episode following her wedding to the Reverend, she burned down their apartment while cooking chicken with the gang locked inside. Everyone panicked except for Rolly, who knew "Thelma's cooking would kill us all one day" and read the newspaper as smoke filled the room and the others made frantic calls to 911.
Basil: It's the recipe for Anil's spring rolls. Stephen: (takes it and reads) Oh, so that's why they're green. Basil: Yes, and it also explains why we only ever have them when Anil has a cold.
In one episode when he temporarily loses the cafe, being an expert in the field of bad food, he becomes the new food hygiene inspector for the local council.
Stephen: What happened to the old one? Anil:(funeral music starts playing) One of my pies.
A pool of his chili sauce can substitute for a Lava Pit.
In another episode, he makes something that actually tastes good (according to the main cast). But then...
Basil: 'Ere, Anil. How did you get rid of those rats in the end? (silence; one by one they stop eating as it dawns on them...)
Barth from You Can't Do That on Television was known to blow his nose in the burger buns. The source of the meat was even worse. Anyone who heard where it came from would vomit. Said vomit was promptly used as sauce.
Airi can brew a mean cup of coffee, but she also makes health foods for her brother Ryotaro that are... less than pleasant. Think "sesame seed milkshake". One episode actually has the two in a spat because Ryotaro called the cops to dispose of one of Airi's stews as a bio-hazard.
Naomi, the waitress on the DenLiner has the opposite problem. She can prepare tasty foods like rice and pudding, but her coffee is a powdery, whipped cream-topped disaster that is only enjoyed by the Imagin.
Jessie: Bertram is always made fun of by the Ross kids for his terrible cooking.
Mako from Samurai Sentai Shinkenger, complete with dubious knife-cutting style (she actually uses her Shinkenmaru to cut the poor veggies!). By episode 25, the sight of her holding an apron has traumatized the Kuroko. The only person who can eat her food and genuinely enjoy it is Kotoha.
The last time she is shown cooking, the Kuroko are standing by with antacids and a stretcher since Takeru was sick in bed for days after the previous time she had cooked. The Kuroko actually have standing orders to keep Mako out of the kitchen at all costs, but she managed to slip past them that time.
Mako's Power Rangers Samurai counterpart Mia is said to be this too with an odd concept of matching ingredients, though Kotoha's counterpart Emily might have the same aversion to it as anyone else, but is aware that people don't like it so occasionally gave warnings. On the other hand, there is someone who enjoys her cooking: Lauren. The difference is that her Sentai counterpart, Kaoru, has never eaten anything Mako cooked and so her opinion was unclear.
Yukito from Bakuryuu Sentai Abaranger. He's a horrid cook, but insists that he's THAT good and forces his teammates to eat his cooking, and if they don't, it's the cooking equivalent to TV Tropes' "You have no soul" for them. Hell, his cooking rendered Asuka to hole up in the toilet for the whole episode.
Maddie Magellan from Jonathan Creek. Perhaps not truly lethal, but upon opening her oven and discovering the contents to be in flames, she declared that it needed "Two more minutes" and closed the oven door again.
The title character of The Sarah Jane Adventures has vast experience with all kinds of alien races, years of travel through time and space, remarkable knowledge of alien technology, and general overall brilliance and awesomeness.....but she can't cook. Although it's not mentioned very often onscreen, her ineptitude in all things culinary is apparently a very common occurrence, given that, by the beginning of Series Four, her son Luke is so accustomed to it that he sends Clyde a text message casually informing him that, "Mum set the kitchen on fire again..."
Jackie from That '70s Show. She rarely tries to cook (as she put it, she was hoping to get on by her looks), but when she does try, the results are disastrous.
In The Nanny episode "Close Shave", C.C. Babcock has been attending a cooking class, and gets Maxwell to try some of her cooking (Fran looked at it, and thought it was dog food.) He reluctantly does so, and spends the entire episode violently ill. Everybody blamed C.C.'s cooking, but as it turns out, it was actually appendicitis. This all leads to a scene where Fran, disguised as a candy striper, is asked to shave Maxwell in preparation for surgery....
Peg on Married... with Children is this in the episodes where she actually does cook (mostly the early ones). Most of the time, the Bundys just eat take-out and fast food (or steal from the neighbors) because Peg is too lazy to cook. Just to show what her cooking can do, In one episode, the Bundy kids won a home concert from Anthrax and 50 of their friends. A blizzard snowed them in. Since they couldn't go out for food, they hit the fridge.
Bud: Well, there's always mom's Foil Wrapped Mystery Pack. (Band scarfs it down) Kelly: Wow, even dad won't eat the Mystery Pack. These guys are cool! Band Members: Whoa, the colors. The colors! / If it just came out of the fridge, why is it hot? / Ow! Mine bit me!
Elvin from The Cosby Show once tried to impress Clair Huxtable by making a chocolate chocolate chip cake that was "extra-dense". It took Cliff a full minute to cut a piece, it weighed down the plate he put it on and he immediately got up and spit the one bite he took into a BIG wad of paper towels. His advice to Elvin:
Cliff: You don't want Mrs. Huxtable to eat that.
Elvin: Well, what do I do with it?
Cliff: I don't know. You're too far from the ocean.
Jeremy Clarkson on Top Gear. See the "Manly V8 Smoothie"/"Desperate Shag in a Skip"/"Bloody Awful" for the best example. Although there is also the time his attempt to make chips on a filmed caravan holiday with his co-hosts Richard Hammond and James May resulted in their caravan and a neighboring caravan burning down. (It later came out that the fire in their own caravan was staged for the show, but the accidental spread to the neighboring caravan was not.)
Uncle Fester of The Addams Family thinks that combining sulfur, charcoal, and saltpeter makes fudge (for those who don't know, that's the recipe for gunpowder).
Oscar from Corner Gas. According to Brent, his homemade beer tasted liked he "beat a skunk to death with a salmon". When Hank is hired to demolish a barn and decides to blow it up, Oscar offers to help him. When Hank asks him what he knows about blowing things up, we are treated to a montage of stuff blowing up in Oscar's face, the last one being a salad.
Hank: How do you blow up a salad?
Oscar: Happens more than you think!
Lightly implied in Doctor Who. Amy Pond's mother brings her breakfast in bed on the day of her wedding, but says that since her father made it she might as well simply throw it out as it is "an atrocity".
My Wife and Kids has Claire, who in one episode tries to cook a chicken for her parents' anniversary by taking said chicken into the oven for hours but forgets to set the switch on to "cook", resulting in the chicken being unfit for human consumption.
Usually averted with Victor from That's So Raven since he's an outstanding chef. But in one episode, he had Cory, Eddie, and Chelsea try out his mother's Pickled Artichoke Mash Potatoes, which didn't taste good at all, and the three tried in devious ways to get rid of the food before Victor found out. In the end, they finally confess, and Victor himself concedes that he hated the recipe himself.
Good Luck Charlie: Amy is known to be such a bad cook to her family so much that in one episode, PJ (who has a talent in cooking) tried to trick her so he can bake the Thanksgiving Turkey instead.
The third series of Horatio Hornblower has Styles, a prominent lower-deck character as Horatio's steward. He attempts to boil coffee and generally renders all his food inedible. Lt. Bush says it best:
Bush: Learn to cook or I'll cook you.
Buffy of Buffy the Vampire Slayer really can't cook, although she eventually learns enough to make a passable Thanksgiving dinner.
Willow: What kind of punch did you make?
Buffy: I made lemonade!
Willow: How much sugar did you use?
Buffy: Sugar? [Willow makes a face and spits it out]
Later... Willow: Cordelia, have some lemonade.
Ralph Malph from Happy Days. When Richie, Potsy and Ralph move out of home to share an apartment, we learn Ralph uses lighter fluid to ignite his cherries jubilee.
In an episode of Too Close for Comfort, Henry's niece April sets up a meeting between Henry and his brother Bill (who is also April's father), to reunite them after years of having not spoken to one another; Monroe decides to make Cheesecake Mischak, a cheesecake with arsenic as an ingredient (the recipe is intended to be used to kill rats) for the occasion, not realizing the cheesecake's intended purpose. Subverted in the fact that Monroe later reveals he left out the arsenic, as he couldn't find it at the grocery store; this is made all the more hilarious, as Henry's brother is taken to the hospital to have his stomach pumped, after he had eaten the supposedly poisoned cake. Bill later finds out, though when Henry tells April, his wife Muriel, his wife Jackie and Monroe not to tell Bill that he had his stomach pumped for nothing.
Malena in For Your Love. There are plenty of jokes about her non-existent cooking skills — for example in one episode, Mel has a daydream of her actually being a good cook, then reality sets in and he finds himself staring at a badly burnt casserole.
Ned's Declassified School Survival Guide: the things the title screen warns you that the guide will help you with is "gross school lunches". The food on the tray routinely crawls off if you take your eyes off of it.
Mythbusters confirmed that you CAN tenderize meat with explosives and safely use C4 explosive as cooking fuel.
Aethelwynne from Pixelface. In "The Game's Up", Aethelwynne promises to prepare some elven delicacies as a treat for Rex's going away party. Sgt. Riely's gift to Rex is a promise to Rex that he'll eat Rex's portion for him.
Tyrion Lannister has brought Camp Follower Shae to the capital against the express orders of his father. He suggests hiding her presence by sending her to the kitchens.
Shae: Every man who has tasted my cooking has told me what a good whore I am.
Brienne learns the hard way that Pod has no cooking experience when he doesn't even know to skin a rabbit before cooking it. And then he manages to set it on fire.
The prison chef on The Slammer passes out after eating some of his own cooking, and the Governor is no better when he attempts to take over the role.
Midsomer Murders: Joyce Barnaby is a bad cook. However, her husband (Tom) and daughter (Cully) humor her and eat her cooking anyway. Joyce's bad cooking seems to be a little private joke between Tom and Cully.
Ria Parkinson in the sitcom Butterflies is possibly the world's worst cook, despite being a homemaking mum with a dentist husband and two grown sons. Her husband remarked that if she fed her lamb cutlets to his patients, he'd be a rich man overnight, and his dental practice would at least triple in size.
iCarly: In "iStill Psycho", Nora's invites the iCarly gang over for a "Norwegian" supper, which is really a very weird mixture of strange things that that the protagonists find difficult to eat.
A special example is Matt's "Exotic Tartare" from Season 4, containing venison, diver scallops, caviar, and white chocolate. Gordon Ramsay takes a mouthful and lasts just long enough to note that there were capers in the dish before doubling over to hurl. Twice. Throughout that season, Matt's teammates tell him to shut up whenever he comes up with a suggestion.
Antonia from Season 8 also made Ramsay vomit with her signature dish, a supposed Mardi Gras Gumbo that looked like "liquid shit", as Ramsay put it. When she got upset "it wasn't up to par", he made everyone else taste it, with such descriptions as "like a big bowl of mud" and "I'd rather have a cat shit in my mouth".
On Dog with a Blog, Ellen is such a horrible cook that other moms started calling her "Smellen".
Evelyn: I was a young bride! No one told me you don't keep fish in a drawer!
The Suite Life on Deck: Zack and Cody always look forward to their mother's blueberry muffins... because they bounce like superballs and make great erasers.
For the most part, Aunt Bea from The Andy Griffith Show is an excellent cook, but everybody seems to really hate her pickles. Opie commented that the make him sick. In fact, they end up literally lethal, at least in the case of bugs.
Bernard: My oven can cook anything... My oven can cook BITS OF OVEN.
Kaoru Mitsuki of "GARO" series Fame's first on-screen attempt at cooking for her friend requires their immediate hospitalization. And it just goes downhill from there.
227: Pearl once entered her rhubarb pie in a baking contest and she not only lost, but made the judges sick. When her grandson Calvin points out that she still makes that pie, she replies "And it's still making people sick!"
Apparently Isabelle Lightwood of Shadowhunters is this, as Jace quips that Simon entering a room full of Muggle-killing runes might be less lethal than consuming her cooking.
Detective Amy Santiago from Brooklyn Nine-Nine seems to be this, as she for example thinks that salt and baking soda are interchangeable, on the principle that they're both white powders.
Victor proves to be one after he cooks breakfast for the students. The breakfast consisted of sticky mush that none of the students could even get out of the bowl or off of the spoon. They decided to get from the vending machines instead.
Jerome once tried to make a special sauce to go with the hot-dogs he and Alfie were using in a recipe contest. It ended up with a messy kitchen, a horrible smell, and Jerome going crazy, prompting Mara to help him.
Arrested Development: Lindsay's thankfully rare attempts at cooking invariably fall under this. She doesn't have even the most basic understanding of food preparation, resulting in dishes such as "hot ham water", and soup made with uncooked chicken. She also has an alarming habit of leaving the stove unattended.
The Netflix series Nailed It! invites lethal chefs to compete in making extravagant desserts, and awards $10 000 to the person who fails the least. While the premise is a bit forced - it would be hard for even skilled bakers to complete some of the challenges in the time allotted - pictures of the contestants' home baking show that nope, they really are that bad. Mistakes made on the show include not cooling cakes before icing them (causing the icing to melt), forgetting to put filling between cake layers (resulting in a very dry finished product), and in one really outstanding case, leaving the actual cake mix out of the batter and putting a mixture of eggs, milk and oil in the oven (the judges intervened on that one).