This article is from the Puzzles FAQ, by Chris Cole email@example.com and Matthew Daly firstname.lastname@example.org with numerous contributions by others.
What is a sentence with the same word several times repeated? Do not use
quotation marks, proper names, a language other than English, or anything
Five "had"s in a row:
The parents were unable to conceive, so they hired someone else to
be a surrogate.
The parents had had a surrogate have their child.
The parents had had had their child.
The child had had no breakfast.
The child whose parents had had had had had no breakfast.
It is arguably possible to construct sentences with arbitrarily many
repetitions of a word. For example:
1. Bulldogs fight
2. Bulldogs bulldogs fight fight.
(i.e., bulldogs (that) bulldogs fight, (themselves) fight)
3. Bulldogs bulldogs bulldogs fight fight fight.
(i.e., bulldogs (that) bulldogs (that) bulldogs fight, (themselves) fight,