Some times I think that children music are my favorites songs. Only listening a little piece it's enough for have the song in my mind for a lot of time, days, even weeks.
This is because children song are made for remembering. They have a simple lyric, a memorable melody and repetitive message ideal for children.
Usually children's song has a simple form, alternating verse and chorus, where the melody are the same in each one. Lyrics in chorus are the samen while changing the message in verses, doing a nice story everything together.