Whatever the reason, the theme of the summer belonged to Mariah Carey's "We Belong Together," which is all about a guy who left her and took a part of her while she begs for him back. Maybe a lot of people were going through break ups in 2005? Or pining for a long lost ex? Doesn't sound like a fun summer song to us. We'd rather be singing about beaches and bonfires, but enough people requested it that it made it to the top of the chart that year.