In the video "Giving Mom Money Every 15 Minutes (Birthday!)" by Ranz and Niana, they celebrate their mom's birthday in a unique way by surprising her with cash gifts every 15 minutes throughout the day. The siblings plan various fun activities and gifts, creating a joyful atmosphere. Their mom's reactions are heartwarming and filled with gratitude, showcasing the love and appreciation they have for her. It's a delightful blend of creativity and thoughtfulness, making for a memorable birthday celebration!