Christian Alexander’s first apartment in New York City was in Bed-Stuy, Brooklyn, and his roommate was filthy. The man’s space was littered with chewed gum, dirty laundry, food, loose tobacco and weed, spare change and dog treats. But none of that compared to what Mr. Alexander — perhaps inevitably — found one day.

His roommate had been housing “an army of maggots,” Mr. Alexander said. “And he didn’t have a clue.”

Roommates can be a great solution to high New York City rents but also a never-ending source of frustration. Borrowing clothes without permission. Eating food without paying for it. Stealing!

Nearly everyone who has started a new life in the city has suffered through a wild roommate situation or two. Now, with limited space, and rents incredibly high and rising, newcomers and people who have been here for years are urgently on the hunt for affordable options. That often involves a roommate. Or two. Or more.

The situation will become more acute in coming weeks, as young people with summer jobs, internships and dreams of exciting new lives arrive in large numbers.

We asked New Yorkers to share their most unforgettable roommate experiences and found that they came in all flavors: horrifying, heartwarming, weird and curious. One person had a fashion-student roommate he described as “a practicing witch.” A woman in Fort Greene, Brooklyn, recalled a roommate with perpetually lost keys who climbed in and out through the fire escape — setting off alarms day and night.