Chicago’s Lincoln Square neighborhood is blessed with Giddings Plaza, a popular spot for summer concerts and food stands. Like any plaza worth its salt, it also has a three-tiered fountain, which has been described by Yelp reviewers as “delightful,” “exquisite,” “intimate,” and “pretty.”

Increasingly, though, another adjective applies: sudsy.

Like all fountains, Giddings Fountain has always experienced the occasional soapy spell. But lately, it’s become a more regular target. According to DNAinfo Chicago, the fountain is now filled with foamy bubbles about once per week.

No one is quite sure who’s doing it. Public response is usually positive, though: “Toddlers squeal, teens lob lather ‘snowballs’ at each other, and grown-ups whip out their phones,” the outlet reports.

Soaping a fountain is a classic prank—it’s cheap and quick, and provides a near-instant payback. In certain instances, it’s also a pain for city police forces and parks departments, which have to spend time and money rinsing the fountain and chasing down any errant foam.

In this case, though, it’s fairly low-impact: Matt Saulka of Fountain Technologies, which services Chicago’s public fountains, told DNAinfo that it hasn’t caused the fountain any harm. “It’s just soap,” he said. “It doesn’t do anything.”

Every day, we track down a fleeting wonder—something amazing that’s only happening right now. Have a tip for us? Tell us about it! Send your temporary miracles to cara@atlasobscura.com.