Enough Is Enough

"Enough Is Enough" was the title to, or significant lyrics from, a 20th century song by Donna Summer and Barbra Streisand. The Doctor once quoted the words when trying to stop a round of bickering between Col and Professor Ty Benson on the planet Sunday. (NSA: Wetworld)
 * In the real world, the song is subtitled "Enough Is Enough", but actually entitled "No More Tears". Wetworld'' offers no firm statement that "Enough Is Enough" is the title, as the Doctor is merely quoting the lyric, and crediting the artists who made it popular.