Flash mobs might not be as popular as they once were (my favorite, 4EVA and always, will be the Bruno-Mars-wedding-proposal-in-the-back-of-a-car one), but they’re definitely still effective. Here’s one that’s both effective and affective: Tessa Prothero, a nine-year-old suffering from a rare brain cancer, was granted one in honor of her birthday.

It was organized by Gilda’s Club of Metro Detroit, an organization with programming for those affected by cancer. Will Thomas, former finalist of “So You Think You Can Dance” and brother of a Gilda’s Club staffer, choreographed the flash mob with the help of two participating local dance studios. It all went down right outside Tessa’s home on Monday: