Some variations of the lyrics used in primary school:

I believe the first originates in the UK and the second is Australian.

Happy Birthday to you,
Squashed Tomatoes and Stew,
Bread and Butter in the gutter,
Happy Birthday to you.

Happy Birthday to you,
You're a hundred-and-two,
You look like a monkey,
and you smell like one too.

Xenex mentions that the second line of the second version above is sometimes "you live in a zoo"