ACathy appears in all of the episodes from the first two seasons. However, she does not appear in four episodes of the third season: Sick in Bed (3.10), Patty Leads a Dog's Life (3.22), A Visit from Uncle Jed (3.26) and Fiancee for a Day (3.30). The episode A Visit from Uncle Jed is the only one that explains her absence.
AMeet Cathy, who's lived most everywhere,
from Zanzibar to Barclay Square.
But Patty's only seen the sights a girl can see from Brooklyn Heights --
What a crazy pair!But they're cousins,
Identical cousins all the way.
One pair of matching bookends,
Different as night and day.Where Cathy adores a minuet,
The Ballet Russes, and crepes suzette,
Our Patty loves to rock and roll,
A hot dog makes her lose control --
What a wild duet!Still, they're cousins,
Identical cousins and you'll find,
They laugh alike, they walk alike,
At times they even talk alike --
You can lose your mind,
When cousins are two of a kind!