"Jeffy's Song" was performed by an unnamed farmer in the Season Eight episode, "You Got F'd in the A". The song is parody of the folk standard "Crawdad Song".
Background
While looking for members for his dance troupe, Stan Marsh heard about a special "dancing duck", named Jeffy. When they meet the farmer and his duck, the duck didn't appear impressive. When the farmer began playing a fiddle, and sang the duck's favorite song, he flapped his wings and strutted around to the music. According to the farmer, Jeffy dances to any song he knows, which are all about drug abuse, sex and domestic violence.
Lyrics
First song:
You'll do a line and I'll do a line, honeeey.
You'll do a line and I'll do a line, babe.
You'll do a line and I'll do a line, we'll fight an' screw 'til the mornin' time.
Honey, babe, be mine.
You'll do a line and I'll do a line, honey.
Second Song:
Same tune as the first.
You'll snort K and I'll snort K, honeeey.
You'll snort K and I'll snort K, babe.
You'll snort K and I'll snort K, we'll fight an' screw all night and day.
Honey, babe, be mine.