The Oinker Sisters are a trio of pigs who have appeared on Sesame Street periodically since Season 17 (1985-1986). Their name is a riff on the Pointer Sisters (who had previously sang on the Pinball Number Count animated segments).
The sisters are best remembered for their song "A New Way to Walk." The leader, Sooey Oinker, is voiced by Ivy Austin, while the other members have changed over the years. Singers have included Heidi Berg and Cheryl Hardwick. In episode 3745, their first names are revealed (despite Sooey being the only name previously mentioned): LaVerne, Louise, and Lutrella.
According to Elmo's World: "Families", "The Days of Swine and Roses" is the title of an Oinker Sisters album.