To see the lyrics, click on the name of the version you are interested in (on the left).

It seems this song hasn’t been played since 2001. Before it had apparently only been played during the ASAAL promo.

If this song contains references to Casanova (horses, frogs and dogs), it is simply because it was recorded for the album Casanova, but it was eventually not considered good enough to be on the album. It was then recorded again for A Short Album About Love.
“Don’t look a horse gift in the month” in an idiom about not being ungrateful when receiving a gift or trying to underrate it. Indeed, wearing and gradient of horse’s teeth enables one to estimate its age. Subject a gift to this examination appears quite tactless.

I don’t know about frogs, but horses and dogs are Neil Hannon’s favourite animals.