In the latest (January 30th) New Yorker, this cartoon by Sam Gross:
Completely wordless — but how much cultural knowledge it takes to understand it! You need to know about doggie/doggy doors (or dog doors, as they’re usually called in the trade), balloon animals, helium, and clowns.
At the other end of the scale there are words-only cartoons, like this Saturday Morning Breakfast Cereal number (opposing social pleasures and stranded prepositions) posted by Mark Liberman a couple years ago:
Cartoons usually have both a picture and a caption (or speech bubbles), but there are limiting cases in both directions: pure sight gags and slogans presented as cartoons, for example.
Now a word on doggie door / doggy door / dog door. The OED has no entry for any of these, or any cites in other entries. Neither AHD5 nor NOAD3 has an entry for any of them. Presumably, the lexicographers on duty at these dictionaries felt that dog door is too transparent — it means ‘door for a dog’, right? — to merit an entry of its own. Well, the referent is a specific kind of door for a dog, so that Wikipedia, rightly to my mind, has an entry for dog door (with illustrations). As Ben Zimmer has said of Adj + N phrases like squeezed middle:
… phrases can be “compositional” while still being invested with special new meanings that lexicographers would rightly want to document. (link)
But now for a twist: from the Wikipedia dog door page, we learn that the corresponding item for cats is called a cat flap (entry here), or cat door, and that the larger category label is pet door – and it turns out that cat-door made it into OED2 (with one cite, from 1959), and that cat flap got added in the draft additions of March 2001 (with cites from 1957 on):
cat-door n. a small door, usually swinging, which can be opened by a cat for its own ingress and egress.
cat flap n. a small hinged flap set into an outer door, wall, etc., which from either side may be pushed open by a cat, allowing it to enter or leave a building; = cat-door
(No entry for pet door, though.)
Why this bias in favor of cats? Wikipedia provides a clue:
Cat flaps are popular in some countries, particularly the United Kingdom where it is believed that about 90% of cats have access to the outdoors.
Equal lexicographic treatment for dogs!