Such happenstance isn’t in itself unusual. The Jenny Slate comedy “Obvious Child” (2014) began as a short that its director, Gillian Robespierre, posted to Vimeo in 2009. She said the short was never meant to be a calling card for a feature, but more of a counterweight to depictions of unplanned pregnancies in other movies. “It was really just a gut reaction to what we felt was lacking in movies and in our culture and in the conversation,” she said.

But word of mouth attracted the attention of Jezebel, one of a handful of news media outlets that praised the short, at around the same time that Slate, who starred in both versions, made her first appearance on “Saturday Night Live.” Robespierre said Slate’s exposure helped to create a stir around the movie, and that the positive response led to the writing of a feature that fleshed out details of the heroine’s job and family. (It also filmed at a Planned Parenthood, as opposed to Robespierre’s mother’s podiatrist’s office.)

“The Babadook” (2014), directed by the Australian filmmaker Jennifer Kent, took an even longer journey from short to feature. It began as a 2005 short called “Monster,” filmed at a time when, Kent said, it was “a miracle to get something made and have it be similar to what was in my head.

“I was inspired by a friend who was having difficulty with her son, who kept seeing a monster everywhere,” she said. “So I had the idea, what if that monster was actually real?”