SpongeBob Squarepants Easter Egg - To the Dump!

In the episode about pollution and global warming in Rocko's Modern Life, after the first spring cleaning song, Rocko and Heffer are taking trash cans to the dump.
Heffer sings: "To the dump, to the dump, to the dump dump dump"

Spongebob sings the same thing when Squidward goes crazy at the end of episode "Artist Unknown":
"Oh well (gets into cereal box) (singing) to the dump, to the dump, to the dump dump dump"

The egg is that Spongebob and Heffer are both voiced by Tom Kenny, and the creator of Spongebob Squarepants, Stephen Hillenburg, used to direct Rocko's Modern Life.