An alternate version of the ABC song that slows down the LMNOP part is currently going viral because of a tweet by Noah Garfinkel: "They changed the ABC song to clarify the LMNOP part, and it is life ruining."
I tracked down the original video from 2012:
The alternate arrangement is by Matt Richelson, who runs a popular YouTube channel and several websites dedicated to offering free materials (songs, lesson plans, etc.) to help kids learn English. Here's what Richelson says about his version of the ABC song:
About the slow l,m,n,o,p: I teach young learners of English as a foreign language, and have found this way the most effective for teaching the letters.
I love the ellemmennohpee bit as much as anyone, but his reasoning is solid.