What's one growth experiment that gave you a result you didn't expect?

I've started paying less attention to "growth hacks" and more attention to small experiments.

A lot of things sound great when you read about them, but once you actually try them, nothing happens.

Then occasionally you run something that takes a few hours and produces a result you weren't expecting.

Could be:

• SEO
• Reddit
• Cold email
• Partnerships
• Product-led growth
• Content
• Paid ads
• Referral loops
• Something completely different

What's one experiment you've run where the result genuinely surprised you?

Would be more interested in the actual experiment + result than a list of generic tactics.