Probably my favorite of the old Merrie Melodies

It's certainly one of the most memorable. Unlike a lot of the others, this one's rights were renewed by Warner, and it appears on the Looney Tunes Golden Collection Vol. 3 DVD set. For this reason, the extant version of the cartoon begins with the Warner bullseye and 'Merrily We Go Along' theme, instead of the one it was probably released with (see Country Boy (1935) and My Green Fedora (1935) for examples of the "I Think You're Ducky" opening).

Piggy, our protagonist, isn't Porky, nor is he an antecedent to Porky (as some have argued that Egghead is the antecedent for Elmer Fudd). He is one of Mrs Hamhock's children, a family introduced to us in At Your Service Madame (1936) http://www.imdb.com/title/tt0027315/, where the children defend their German-accented mother against the pecuniary interests of a W.C. Fields pig. It's been suggested that the Hamhock children were at one point intended to represent the Seven Deadly Sins, with Piggy (or Sonny, as his mother calls him at one point) standing in for Gluttony, but that Leon Schlesinger did not approve.
http://encycl.opentopia.com/term/Pigs_Is_Pigs_%281937_film%29

This cartoon has been the subject of many homages and parodies.

YouTube version of Pigs is Pigs:
http://www.youtube.com/watch?v=iXI8d37KCS8

Pigs is Pigs is the 3rd Warner cartoon of 1937, released on Jan.30th of that year.

It is preceded by Porky the Wrestler
http://www.imdb.com/title/tt0029422/
...and followed by Porky's Road Race
http://www.imdb.com/title/tt0029430/

§« The Sleep of Reason Produces Monsters. »§