Greta Gerwig’s “Barbie” elevated a Mattel-produced toy adaptation into a work of art that drew near-universal acclaim — but extended references to the one most famously difficult writers in modernist literature were still a bridge too far for test audiences.

One of the funniest sequences in the film takes place when Margot Robbie’s eponymous doll meets a group of so-called “Weird Barbies,” many of whom are references to real ill-advised dolls that Mattel produced over the years. Gerwig previously told IndieWire that the scene originally featured a joke about a fake Barbie inspired by Marcel Proust, the French writer whose sprawling epic “In Search of Lost Time” is considered one of the most challenging novels ever written

“I think I got most of them in there,” Gerwig said when asked about alternative Barbies that didn’t make the final cut. “We did have a more extensive thing that...