Sorcha, I remember watching a documentary where monkeys were getting drunk. It may well be connected to this article from the BBC.

I've never seen an animal get drunk first hand but I do know a dog who is particularly partial to the head of a pint of Guinness (but will take other beers) you may have met. I can't remember whether Ben (a German Shephard sort of golden lab coloured) was in the pub the night you encountered "the rudest woman in the world". I will often dip my finger in a glass and let him lick it but Ian (the owner) sometimes puts a small amount (probably less than 1/8 pint to 2 pints water) of his Guinness into the water bowl and Ben seems to love it.