Songfacts®:

• When the Cole Porter musical Paris opened in Atlantic City on February 6, 1928, it included a song called "Let's Misbehave." This was shortly replaced by "Let's Do It," which is also known as "Let's Do It, Let's Fall In Love" or "Let's Do It (Let's Fall In Love)." According to Porter's biographer George Eells, "In opting for the latter, Cole discovered that there was infinitely more humor in a provocatively insinuating proposal than a direct proposition."
• Paris was the first of Porter's hit shows, and "Let's Do It" - though not the first of his "list songs" - remains one of his finest; it was performed on Broadway by Irène Bordoni. Originally, the chorus included "Chinks do it, Japs do it," but this was soon changed to "Birds do it, bees do it."
• "Let's Do It" has been covered by many artists over the years, including Porter's great rival Noël Coward. According to the Noël Coward Society, "The Master" began performing the song during the Second World War when he was anxious to establish a large repertoire of comedy numbers for entertaining the troops. With Porter's permission, he rewrote the lyrics with personalized versions for almost every audience.
• Coward's most alluring rendition was delivered during his season at the Desert Inn, Las Vegas. On June 8, 1955, he wrote to his friend Lorne Loraine:
  
  "The high spot, as usual, was 'Let's Do It' at the end, for which I have written an extra chorus full of local allusions, all of which tore the place up."
  
  As with many of Coward's songs, he came close to crossing the line, here with "Even Liberace we assume does it." Two years later, Liberace would sue the British Daily Mirror newspaper over insinuations of homosexuality. Coward's Desert Inn version of "Let's Do It" also includes the alluring couplet:
  
  Teenagers squeezed into jeans do it
  Probably we'll live to see machines do it... >>

  Suggestion credit:
  Alexander Baron - London, England, for all above
• Alanis Morissette performed this in the 2004 Cole Porter biopic, De-Lovely, named for the Porter song.