Not really a holiday, but...
I’m a musician, and went on a recital tour of Spain last summer. During the trip, the following happened:

I packed a digital metronome in my hand luggage. You can imagine how amused customs were when it switched itself on and started bleeping at 60 beats per minute.

I came down with flu within 24 hours of arrival.

My pianist was suicidal for the entire trip.

My concert organiser was the creepiest man I have ever had the displeasure of meeting - decided early on that I needed a “father figure“ and set about trying to adopt me. I found out later that he hadn’t seen his own daughter since his divorce eight years previously.

On a long journey, we hadn't come across any form of civilisation for hours and I desperately needed to take a piss. Finally we came across a bush, I dashed in there, dropped my trousers, and discovered all too late that it contained a hornets' nest. And hornets don't take kindly to being pissed on.

We were served stewed pigs’ trotters by a naked arts’ councillor.

At the same gig, we were expected to play outside. At 9pm. In the middle of summer. Near a stagnant pond. Cue every biting insect known to man, in addition to a snake who crawled across the stage halfway through a Beethoven Sonata.

As soon as I got over the flu, I got a migraine that lasted the rest of the trip. Cue puking my guts out in the only toilet at a nasty service station in the Pyrenees, with a bunch of disgruntled Spanish truck drivers yelling at me to hurry up.

Nothing could go wrong once we’d got on the plane back home, right? Wrong! Picture the scene: A mad Cuban brandishing a knife and talking about the “extremo del mundo”, a bunch of American tourists screaming, “We’re all gonna diiiiiiee!” and eight Guarda Policias armed with bayonets removing the offending nutcase. God only knows what would have happened if he’d only made an appearance after the plane had left the ground.

Ah well, at least I got paid at the end of it.
(grandmasterfluffles Come to my Armageddon party on, Sun 24 Apr 2005, 12:15, Reply)