This is a parody of Fat Albert & The Cosby Kids, a program that aired in the late 1960s and early 70's, and is not confused with the 2005 movie of the same name. Like Fat Albert and the Cosby Kids, they had a junk yard band.
Background
This show is the third of many that Timmy Turner visits in "Channel Chasers", after wishing for a Magic TV Remote that allows him to travel through television as if the programs were real worlds. After arriving and asking to join the band, Timmy was given what looked like a street sweeper with a string to play. However, one of the characters revealed that it was actually the "pooper scooper" to Timmy's surprise.
Trivia
Heavy Hal's "Yo, yo, yo" catchphrase is spoken like Fat Albert's "Hey, hey, hey" catchphrase.
Timmy's appearance in Heavy Hal is a mix of Dumb Donald and Mush Mouth from Fat Albert.
