Funny item co-occurrences in 3 million Instacart orders

The other day I was idly wondering what are the strangest combinations of items people buy at grocery stores. The kind of shopping cart that makes the cashier snicker and later tell his friends, "Dude, can you believe this guy came in and only bought condoms and apples?"So I fired up Claude and started looking for any receipt data I could find.For the final results, scroll to the bottom. Otherwise, read on to follow the journey.Grocery stores keep this kind of data very close to the chest. There are consumer apps that collect receipt data (like ReceiptHog and Fetch) but they presumably just sell it to hedge funds or something. Years ago, however, Instacart open-sourced data from 3 million orders as part of a machine learning competition to optimize their recommendation algorithm. The data is still available on Kaggle and it's very rich. What we want is the exact opposite of a recommendation algorithm but this data should work fine.The Instacart data set includes the following:3,214,874 orders~10 products per order on average49,688 unique products134 unique "aisles" (product categories)So all we have to do is look at every cart and see which combinations of items are least likely to appear, right? Let's try that. For the sake of testing a few groupings, I included pairs, triples, and quads.Product co-occurrence count: pairs

count   product 1 product 2

1 Banana Extra Fancy Unsalted Mixed Nuts

1 Organic Hass Avocado Baby Cucumbers

1 Organic Hass Avocado Trail Mix

1 Bag of Organic Bananas Bananas

1 Limes Trail Mix

1 Organic Garnet Sweet Potato (Yam)   Clementines

1 Organic Avocado Zero Calorie Cola

1 Organic Fuji Apple Baby Cucumbers

Note: maximum pair co-occurrence count is 62,341.Product co-occurrence count: triples

count   product 1   product 2 product 3

1 Banana Bag of Organic Bananas   Soda

1 Banana Bag of Organic Bananas Clementines

1 Banana Bag of Organic Bananas Sparkling Mineral Water

1 Banana Bag of Organic Bananas Flat Parsley, Bunch

1 Banana Bag of Organic Bananas Sparkling Water

1 Banana Bag of Organic Bananas Fresh CA Grown Eggs

1 Banana Bag of Organic Bananas Red Seedless Grapes

Note: maximum triple co-occurrence count is 15,066.Product co-occurrence count: quads

count   product 1   product 2 product 3 product 4

1 Banana Bag of Organic Bananas   Organic Baby Spinach Half & Half

1 Banana Bag of Organic Bananas Organic Whole Milk Organic Zucchini

1 Banana Bag of Organic Bananas Organic Avocado Organic Half & Half

1 Banana Bag of Organic Bananas Strawberries Organic Lemon

1 Banana Bag of Organic Bananas Organic Hass Avocado   Spring Water

1 Banana Bag of Organic Bananas Organic Yellow Onion Organic Fuji Apple

Note: maximum quad co-occurrence count is 3,828.Hmm. These aren't very interesting. Maybe that's because there are a ton of combinations that only occur once, and we're only looking at the top 5-10, so we need a better way to sort them.There are roughly 1.2 billion possible unique pairs of products (unordered pairs from a set of 50,000). About 97% of them never occur in our data, and of the ones that do, around 22 million pairs occur exactly once. When almost every pair is tied at zero or one, "least common" becomes meaningless.

So how should we sort? Claude had a good idea to rank each combination by "lift": how frequently it actually appears divided by how frequently we'd expect it to appear. If you have two very common items like apples and oranges, you'd expect them to co-occur a lot. If they don't, that's notable, and the pair should rank higher. Now let's try that.Product co-occurrence by lift: pairs

lift product 1 product 2

0.0007   Banana Extra Fancy Unsalted Mixed Nuts

0.0010 Organic Hass Avocado Baby Cucumbers

0.0012 Organic Hass Avocado Trail Mix

0.0017 Bag of Organic Bananas Bananas

0.0019 Limes Trail Mix

0.0020 Organic Garnet Sweet Potato (Yam)   Clementines

0.0021 Organic Avocado Zero Calorie Cola

0.0025 Organic Fuji Apple Baby Cucumbers

Product co-occurrence by lift: triples

lift product 1   product 2 product 3

0.0016   Banana Bag of Organic Bananas   Soda

0.0019 Banana Bag of Organic Bananas Clementines

0.0032 Banana Bag of Organic Bananas Sparkling Mineral Water

0.0043 Banana Bag of Organic Bananas Flat Parsley, Bunch

0.0047 Banana Bag of Organic Bananas Sparkling Water

0.0056 Banana Bag of Organic Bananas Fresh CA Grown Eggs

Product co-occurrence by lift: quads

lift product 1   product 2 product 3 product 4

0.0111   Banana Bag of Organic Bananas   Organic Baby Spinach Half & Half

0.0128 Banana Bag of Organic Bananas Organic Whole Milk Organic Zucchini

0.0137 Banana Bag of

Organic Bananas Organic Avocado Organic Half & Half

0.0148 Banana Bag of Organic Bananas Strawberries Organic Lemon

0.0155 Banana Bag of Organic Bananas Organic Hass Avocado   Spring Water

I think I see a pattern... Of course it's unlikely that someone would buy both organic and non-organic bananas which points to the bigger issue that 50,000 products is too granular. Every product has a dozen+ variants. There are 28 different condom products and 110 different apple products in the produce department alone, so our silly "condoms + apples" example will struggle to rise above the noise.We have 49,688 products (too narrow) sorted into 134 aisles (too broad). We need something in between. Time to build a classifier! But how?Enter GPCIt turns out nearly 100% of grocery retailers use a product classification system called GS1 Global Product Classification (GPC). GPC is an ontology of everything you might find at a big-box or a grocer. It divides the universe of products into segments (camping, footwear, lighting, tools, food…), which contain families (bread, beverages, fruits, meat, vegetables…), which contain classes (beans, melons, peppers, fungi…), which contain bricks (chanterelles, enokitake, truffles, morels…).Some bricks go even deeper into subtypes or attributes, e.g. Morels can have a growing method of CONVENTIONAL or ORGANIC, but for our purposes we can stop at the brick level. There are 5,318 bricks in the full GPC system. Many segments (plumbing, live animals, industrial systems, etc.) aren't sold at grocery stores, so we can drop them. That leaves 9 grocery-relevant segments with 1,697 total bricks, and our products only populate about 1,000 of them. This feels like the right level of granularity and yields a 50x reduction in complexity!Time to fire up the ol' classifier.

Since we're squeezing ~50,000 products into ~1,000 bricks, I used a standard two-stage approach:Shortlist the brick options for each product. First, get embeddings for every product and every brick. I did this locally using qwen3-embedding:8b. Then, for each product, find its 10 nearest bricks by cosine similarity.Choose the best brick. Use an LLM to select the best-fit brick for each product from the 10 options. This cost me ~$5 and took a few minutes, running 60 requests in parallel using gpt-4.1-mini. The full product-to-brick mapping is here in case it's useful to anyone else.Now let's run our co-occurrence algorithm again and see if using bricks rather than products yields better results.Brick co-occurrence by lift: pairs

lift brick 1 brick 2

0.004   Wine – Still   Grains/Cereal – Not Ready to Eat (Frozen)

0.007 Spirits Grains/Cereal – Not Ready to Eat (Frozen)

0.012 Beer Baby Leaves

0.013 Spirits Dates

0.019 Wine – Still Stem Vegetables (Fresh Cut)

0.020 Spirits Fish – Unprepared/Unprocessed

0.022 Beer Fish – Unprepared/Unprocessed (Shelf Stable)

Brick co-occurrence by lift: triples

lift brick 1 brick 2 brick 3

0.014   Cheese Wine – Still Frozen Grains/Cereal

0.019 Milk Savoury Grain Meals (Shelf Stable)   Spirits

0.019 Cucumbers   Baby/Infant Specialised Foods Spirits

0.020 Kale Clementines Wine – Still

0.021 Broccoli Baby/Infant Specialised Foods Spirits

Brick co-occurrence by lift: quads

lift brick

1 brick 2 brick 3 brick 4

0.027   Banana Strawberries Garlic Spirits

0.028 Milk Substitutes   Strawberries Carrots Spirits

0.032 Banana Milk Substitutes   Baby Food Spirits

0.035 Banana Milk Wine – Still   Savoury Grain Meals

Far less repetition! But there's still something missing. Just because these are the rarest combinations doesn't make them interesting. For some reason people don't buy wine and frozen rice together, or beer and fish. So what? How do we make these combos spicier? Funnier?We need a humor index for products.What's funny?Claude dutifully scored all ~1,000 grocery bricks with a 0–1 humor score, based roughly on how taboo they are or how likely they'd be to come up in a stand-up comedy routine. The general ranges:

score # of bricks examples

0.0 – 0.1 726 Milk, Armenian Cucumber, Herbs, Prepared Fish

0.1 – 0.3 271 Confectionery, Cooking Wines, Breath Fresheners, Ear Care

0.3 – 0.5 50 Energy Drinks, Toilet Paper, Denture Care, Diet Aids

0.5 – 0.7   12 Wart/Corn Treatments, Foot Care, Medical Lubricants, Appetite Control

0.7 – 1.0 15 Condoms, Intimate Lubricants, Contraception, Enemas/Douches

(Humor scores for all bricks are here)Now we can multiply each combo's aggregate humor into the ranking alongside its rarity, and we should get much better results. Let's try that.Funniest rare combos: pairs

brick 1 brick 2

Garlic Diarrhoea Remedies

Kale Enemas/Douches

Garlic Enemas/Douches

Flat Parsley   Condoms

Baby Food Enemas/Douches

Coriander Enemas/Douches

Baby

Food Condoms

Baby Food Adult Diapers

Funniest rare combos: triples

brick 1 brick 2 brick 3

Cheese   Almond Milk Intimate Lubricants

Milk Almond Milk Intimate Lubricants

Apples Avocados Intimate Lubricants

Onions Raspberries Antacids/Flatulence Remedies

Apples Tinned Vegetables   Condoms

Milk Almond Milk   Enemas/Douches

Funniest rare combos: quads

brick 1 brick 2 brick 3 brick 4

Milk Almond Milk   Tomatoes Antacids/Flatulence Remedies

Apples Avocados Ice Cream   Antacids/Flatulence Remedies

Cheese Milk Apples Condoms

Bananas   Apples Kale Antacids/Flatulence Remedies

Bananas Yogurt Milk Enemas/Douches

Much better! Some of these even made me laugh out loud. Kale and an enema? Parsley and condoms? Adult diapers and baby food? There's gotta be a joke in there somewhere.That said, in a large enough shopping cart, funny combos become more likely just by chance. If you're ordering all your groceries for the week you're going to pick up everything, from the boring to the spicier. So what happens if we look only at small carts, where the entire order is just 2 or 3 items?Funniest small carts: 2 items

item 1 item 2

Vitamin D Milk Ultra Thin Condoms

Cola Ultra Thin Condoms

Bag of Organic Bananas Anti-Diarrheal

Italian Bread Ultra Thin Condoms

Oreo Chocolate Sandwich Cookies   Personal Lubricant

Bag of Organic Bananas Incontinence Underwear

Funniest small carts: 3