The Hi-Five song "Birthday Girl" is a special tribute to a girl's birthday. The lyrics express the artist's love and appreciation for his significant other and the importance of celebrating her special day. He promises to make it a night to remember and shower her with affection. The song acknowledges the uniqueness of their relationship and how she holds a special place in his heart. The lyrics emphasize the love and devotion he feels for her and how she is the most important person in his life. Overall, the song is a romantic tribute to the birthday girl and a celebration of their love for each other.