When the boys visit the South Park Genetic Engineering Ranch in an attempt to cross the DNA of Cartman's pot-bellied pig Fluffy and Kyle's Elephant, Dr. Mephesto tells them that doing so is impossible, and that pig and elephant DNA just won't splice. He then mentions that the 1980s pop rock band 'Loverboy', (purportedly) wrote a song about it, which he then performs, with his assistant Kevin acting as a dancer.
Later on, the boys tell Chef about their unsuccessful attempt to create a pot-bellied elephant, and Chef also begins to perform the song, but stops halfway upon realizing that a pot-bellied elephant is a good idea, and tells the boys that since genetic engineering is out of the question, the only way to create one is to get the elephant and Fluffy to make "sweet love."
Da'n Do-A, pig and elephant D-N-A
just won't splice!