This Old Grouch is a resident of Grouchland USA. He 1st appears amongst the Grouch throng in "Welcome to Grouchland". His lines from the song are:
If you're growin' old & love the cold
Spend your golden years in Grouchland
Where the streets are paved in solid mold
& the stinkbugs sing! Sing!
The Grouch Dog can be seen next to the Old Grouch. It can also be assumed that he joined Oscar the Grouch's oratory into action against Huxley, like all the other Grouches to stop him from taking any more of their precious trash from them.