The unusual formation of the list caught my attention. Normally, a three-item list would be formed thus:
x, y(,) and z
Not like this:
x and y and z
It’s also a strange list of creatures that neither have something in common nor form a representative set.
It reminds me of a song my father would sing to me when I was little, called The Unicorn.
Here’s the Wikipedia page and a blog post that has the original poem, a nice little history, and a video of the song. The story is that unicorns played around too long and were left off of Noah’s Ark.
Variations of the following stanza appear throughout the work, functioning poetically as repetition and in the song as a chorus or refrain:
There was green alligators and long-necked geese
Some humpty-backed camels and some chimpanzees
Some cats and rats and elephants, but sure as you’re born
The loveliest of all was the unicorn
Source: The Unicorn,
A Poem by Shel Silverstein, Recorded by the Irish Rovers
There is some unconventional grammar throughout, so don’t take that as a good example of formal speaking or writing. This is probably the best clue we’ll get as to the nature of the reference.
There is probably a second layer that explains the frogs, but the rest is at least plausible. This was a very popular song in its time, and could provide material for humor or otherwise meaningful reference.