How have you instantly won over a partner’s family?

The first time I met my wife’s family was at a family birthday party. As soon as we walked in her SIL screamed that her baby was choking. Everyone froze. I worked several years as a lifeguard, so I immediately ran over to the baby and did the baby heimlich maneuver and a finger sweep and pulled a small pebble out of her mouth. Baby started breathing and crying and was fine. Everyone started asking who I was and thanking me. This also instantly won over my now FIL, who had been notoriously skeptical of people his kids were dating. Worked out great.