Cartoon prototypes
In The Conlanger's Lexipedia, Mark Rosenfelder (Zompist) writes: "(I might add that if you ask a cartoonist to draw it, they’ll probably draw the prototype. From this we can learn that the prototypical hunk of cheese is Swiss, with really big holes.)"
Taking on this, here are the cartoon prototypes -- the way a typical member of various types of things or people is stereotypically drawn -- for many nouns.
Foods
Cheese
A hunk of Swiss cheese, with big holes
Apple
A bright red apple, probably a Red Delicious, with long stem and sometimes a worm
Egg
White, oval hen's egg, no spots
Ice cream
A perfectly conical, hatched cone with big scoops of vanilla ice cream on top
Pizza
A circle of cheese and red pepperoni pizza, with one slice being taken out
Hamburger
Tall, has a sesame seed bun with lettuce and tomatoes decked around the patty
Taco
Hard-shelled, with cheese, lettuce, tomatoes, and beef
Sushi
A squircular piece of shiny, white rice with pink ambiguous seafood inside
Grocery bag
Always has a loaf of French bread sticking out
Hot dog
Red/pink color (cooked but not grilled), with ketchup and mustard
Doughnut
Round and brown, with hole in middle (not a jelly doughnut); often has sprinkles
Toast
Dark brown slice of bread in toque shape, covered with jam and a thick square of butter in the center
Cherries
Duo of bright red cherries connected by conjoined stems
Banana
Peeled open quite a bit, darker yellow peel and lighter yellow flesh
Soda
In can with pop top and design with sinuous curve or spot
Vehicles
Airplane
Plump and white, with a big puffy contrail coming out the back
Car
Bright red, fast
Noah's Ark
A brown wooden boat (not a box as in the Bible), with animals sticking their heads out of the windows and some on the deck; giraffes and elephants will ALWAYS be present
Fire engine
Fire engine red in color, number on side, ladder visible
Schoolbus
Yellow, many windows, kids inside sticking their hands out frantically and many of said kids smiling
Taxi
Checkered with white and black
Bicycle
Usually a boy's frame instead of a girl's frame regardless of the gender of the cyclist, basket in back (often with cat riding inside), decorative bells
Flying saucer
Classic double-saucer shape, metallic color, lurch of fire coming from below (if flying through space) or tripod sticking out (if landed), often has occupant (who is a prototypical Martian or prototypical Grey) -- or duo or trio of aliens of differing heights -- visible inside
Clothes
Pajamas
Vertical red and white stripes
Tie
A solid red, full-width necktie
Natural nonliving objects
Moon
A yellow crescent moon, sometimes anthropomorphized as sleeping
Sun
Yellow, with rays of sunshine emanating from all around, often anthropomorphized as smiling
Star
Yellow, five-pointed
Cloud
A white, puffy cumulus cloud
Lightning
Yellow bolt, forms regular zigzag shape
Diamond
Blue, cut in rhomboid shape, glowing
Animal artifacts
Nest
Brown, round, made of thin twigs, has two to four eggs in it, inhabited by songbirds
Cobweb
Octagonal, like an orb spider's web
Animals
Bird
Songbird perching and singing a song (a bird seen at a distance, on the other hand, will be just a V, like the typical seagull)
Monkey
Brown, hangs from tree by versatile tail, funny/jocular expression on face
Cow
A Holstein cow, with cowbell
Horse
Brown with a black mane
Dinosaur
A big, green sauropod
Pig
Peach-like pink color, little hair, has some mud on it in which it rolled around
Sheep/Lamb
Very fluffy, with white wool
Goat
Thin, white fur, yellow horns, beard
Duck
White (unless it's a rubber duckie, in which case it'll be yellow), orange beak open with an enthusiastic quack, waddling on orange webbed feet
Hen
Reddish-brown feathers, proudly broody or gossipy expression, often pecking at feed
Rooster
Thin, more colorful than hen, erect red wattle, in crowing position, perched atop fence or roost
Chick
Yellow, fuzzy, mouth open in peep, often still has part of the eggshell attached to it
Snake
Long, green, no fangs, like a python, often coils up like a spring
Rabbit
Cute, white, has pink ears; drawn with teeth visible; if there is any food in its mouth, it will be munching on a carrot
Mouse
Grey, in scurrying position, long tail, eating a piece of Swiss cheese
Rat
Grey, fat, long nose, whiskers
Hamster
Light brown/golden color, harried expression, riding on a hamster wheel
Guinea pig
Fat, spotted (with either the spots/patches or the main color being some shade of brown)
Parrot
Predominantly green with some red, mouth open to talk (or eat cracker), perched on somebody's shoulder or cage perch
Parakeet
Green-and-yellow color morph; like the parrot, will be perched on shoulder or cage perch
Seagull
White, fluffy down, in mid-flight with its wings making a V
Lizard
Green, sticking its tongue out to hiss at you
Alligator
Green, yellow underbelly, mouth wide open waiting to snap
Bear
Brown (probably a European brown bear), eating honey
Whale
Blue-grey in color, tail up, smiling, spouting a big spout of water from its blowhole
Fox
Red/bright orange, white tp of tail, prancing, with a crafty expression on its face (probably licking its lips)
Supernatural or mythical beings
Alien
A Grey with white skin and black eyes, lanky build
Martian
Green, antennae, squat build (mostly torso), number of eyes other than two
God
Man with white hair, white moustache, and long white beard
Devil
Red skin, caprine horns, arrow-shaped tail, hooves, carries a pitchfork, devilish look on face, black beard
Witch
Green skin, pointy nose, warts, often cachinnating, black robe and pointy black hat, rides broomstick with black cat as a familiar
Wizard
Older man with white hair and a copious white beard, blue or periwinkle robe, carries wand, wears crumply conical hat with moons and/or stars on it
Fairy
Small, female, wears dress, insect-like wings, playful expression on face, carries wand, slender
Fairy godmother
Same as fairy except older and overweight
Angel
White robe, white bird-like wings, either has a pageboy or medium-length curly hair, serene expression on face, carries harp
Vampire
Fangs, black hair in an Ivy League cut, thin build, black Dracula-style cape, skin is either white and pale or an inhuman green
Unicorn
White with golden horn, often has rainbow mane or creates rainbow colors in its wake
Superhero
Thin, wears spandex, cape on back often adorned with initial of superhero name (even though not all heroes wear capes), often seen flying through the air at quite a velocity
People
Baby
In diaper, big head, pink skin, one tooth, little hair, hairbow if a girl, crying loudly
Boy (child)
Blue eyes, red-and-white-striped T-shirt, blue jeans, sneakers, baseball cap, a little on the fat side
Girl (child)
Blonde hair in pigtails, blue eyes, pink dress, carries doll or teddy
Boy (teenage)
Brown hair is loose and messy, blue eyes, freckles, either a red-and-white-striped T-shirt or a polo with green and blue stripes or blue with one thick white stripe across the middle, skinny
Girl (teenage)
Blonde hair in ponytail, blue eyes, freckles, pink sweatshirt, blue jeans, prominent breasts
Young man (twentysomething)
Black hair, beard, black clothes, looks like a millennial hipster
Young woman (twentysomething)
Blonde hair in ponytail, physically fit, black tank top, prominent breasts
Grandmother
Grey hair, bifocals, smiling face, missing teeth, sweater, sitting in rocking chair
Grandfather
White hair, long white beard, wrinkled, body hunched over, angular body, plaid shirt and coat, carries walking stick
Doctor
Wears band with circle over head and lab coat, carries either stethoscope or tube of miracle medicine
Pirate
Jolly Roger cap, eye patch, red-and-white-striped T-shirt, hook for hand, peg leg, parrot on shoulder, beard
Burglar
Long-sleeved shirt with horizontal stripes, raccoon-like mask over eyes, carries a bag with a dollar sign on it
Basketball player
Very tall, African-American, good-looking, wears shorts and numbered tank top in matching colors
Quarterback
White male, large hunk build, wears shoulder pads, numbered football uniform, golden smile, princely good looks
Soccer player (male)
Hispanic, physically fit and energetic-looking, shiny black hair, dressed in team's colors
Soccer player (female)
Shiny black hair in ponytail, physically fit and energetic-looking, dressed in team's colors
Tennis player
Black hair, head band, polo shirt and preppy clothes, thin, ponytail if female
Baseball player
Vertically striped button-up shirt, forward-facing baseball cap, eager look on face that evinces an "in it to win it" spirit, in shape but neither short nor tall
High school/college jock
Wears letterman jacket (which have been out-of-date on real high school jocks since the nineties), carries football under arm, tall, well-built, head turned up into the air
Scientist
Older Caucasian (usually White but often Jewish) male with messy white hair, unkempt appearance, white lab coat, glasses
Housewife
White woman with medium-length curly red hair, average build, white blouse, blue apron with white polka dots on it, often runs vacuum or carries tray of baked goods right out of the oven
Dad
White man with dark hair in businessman hairstyle, slippers, smokes pipe, grey suit, tie (which he probably got for Father's Day)
Metalhead (or heavy metal musician)
Light brown hair in mullet, edgy look on face, black T-shirt with logo of metal band, spiky metal jewelry
Opera singer
An overweight Nordic woman with a big, open mouth and a Viking hat, dressed in black, cups shaped like round shields over breasts
Cop
Overweight, male, wears blue uniform with eight-point hat and police badge in the shape of a golden shield (or seven-point star if a sheriff)
Villain
Black hair, vaguely non-WASP-looking (either Italian, or Mexican, or Eastern European), black villain moustache, black clothes, menacing grin
Psychologist
Teutonophone or Jewish man, grey hair, prominent beard, wears sweater, has hand up to lips
Butler
Gaunt, in black tailcoat, carries tray
Fitness trainer
Young woman with blonde ponytail, top is either white or black and other clothes are black, a lot of skin showing
Coach
Burly man with whistle around neck
Nerd
Dull brown hair and brown eyes, thick-rimmed glasses, acne, dress shirt with pocket protector, suspenders & bow tie, pants pulled high up, often wears propellerhead beanie
Neckbeard
Middle-aged White male, obese, unruly facial hair, acneous, junk-food-encrusted face, pasty skin, wears either a black T-shirt or a plus-size football jersey with number on it
Mortician
Dressed in black, thin and, well, cadaverous, short stick-up black hair, lots of stubble, morbid expression with visible teeth
American Indian chief
Beige clothes made of animal hides, feathered headdress, stripes of paint on face, tall face with thoughtful expression, carries peace pipe
Professor
Big balding head (the "egghead" look), black mortarboard cap and black clothes, carries pointer, wears glasses, has in-the-air look (often with eyes closed)
Bully
Male, large, very big chin/jaw, hair is either messy or very short
Chef
European man wearing a white top with no pockets and a white toque, fat, thin black moustache
Gangster (Interbellum-era) or Mafioso
Pinstripe suit, black hair, sunglasses, smokes cigar
Detective
Brown trenchcoat, deerstalker, moustache if male, constantly carries magnifying class of front of him/her
Surfer
Long, straight, blonde hair, suntan, wears beach clothes or PacSun T-shirt
Cowboy
Brown cowboy hat, plaid shirt, bandanna, chaps, skinny and bowlegged
King
Crown, imperial beard, wears robe with fur coat, holds sceptre, well-fed
Queen
Woman with brown or red hair, crown, wears dress with fur coat, holds sceptre, well-fed
Jester
Wears caps-and-bells, elf-like shoes, particolor clothing, is laughing out loud
Clown
Rainbow wig, white face paint, big red nose, cheeks painted red, ruffles on clothing