I worked for a time as a teacher for three days of the week at a part-time academy.  I taught children ages 4 through 8.  As they were learning some math skills, I noticed there were many of the children who had difficulty figuring out which numbers were even and which ones were odd.   So, I created this fun-to-sing song that stuck in their minds.  After I taught them the song, there were no more problems with differentiating between even and odd!