I searched for this to verify the lyrics, but didn't find it anywhere (not even Google). I remember it as:

I've been having trouble meeting Mary/
'Cause Mary's ma and pa don't care for me/
So to save a fight and keep everything alright/
I've been meeting Mary at the zoo.

On Monday I met Mary at the camels/
'Cause Mary likes the animals, you see/
Tuesday by the bears and Wednesday by the hares/
And Thursday by the deer my dear you see.

On Friday I met Mary by the monkeys/
Swinging on their little rings of brass/
And Saturday I met Mary by the don-keys/
And that's where I got Mary by the . . . as you desire/
And that's where I got Mary by the zaz-ooo-zazzzz.