Filthomena

 Filthomena  is, obviously , a Grouch  who attends  Oscar  's annual  Grouch  Reunion in the 1989  book   What's in  Oscar  's  Trash Can  ? &amp; Other Good - Night Stories . She also swims in Oscar  's pool at the reunion with  Grundgetta,  Oswaldo  &  Fluffy.

 Filthomena  eventually plays in  Oscar  's Junk Band  also, in the 1994  book   Oscar  's  Grouch  Jamboree  & they sing the  song   Oscar  's  Junk Band .

Books

 *  What ' s in  OSCAR  ' s  TRASH CAN  ? &amp; Other Good - Night Stories  ( 1989 )
 *  OSCAr  ' s  Grouch  Jamboree  ( 1994 )