When a musical artist becomes popular, they can usually release songs on albums as well as singles. They can do this because their songs will sell over and over again because they’re so popular. There are some songs that are not released as singles. For Bruno Mars he has many songs that he is written and released the most of them are singles. Some of these songs include the other side, and rockets here, and runaway baby.
The other side is from the album it’s better if you don’t understand and features Cee Lo Green and BOB. This is probably his best song that wasn’t released as a single in my opinion. This is because it was a collaboration done with two other great artists.