Elmer and the Tune (2017) is a children’s book written by David McKee
When Rose meets Elmer, she’s humming a tune that she cannot get out of her head. When she leaves, Elmer realises he cannot get the tune out of head either. As he crosses the jungle he sees the infectious tune spreading to every animal Rose has met. Once all of the animals have sung the tune, which turns out to be Happy Birthday, it is gone from their heads, but they can now no longer remember the tune.