Referenced in Jimmy Buffett's song "Pencil Thin Mustache": "Writin' fan letters to Sky's niece Penny".
There were two "Songbirds" used in the series--the first was a Cessna T-50 Bobcat, the second was a Cessna 310B.
The T-50's used in the military were referred to as "Bamboo Bomber" because they were made mostly of wood. The first "Songbird" was one of these planes repurposed for the TV show.