I once crocheted a bikini for the shop window. I added a beach ball and my husband made a sign reading NAUGHTICA in the same font as a major fashion design company. The thing turned out to be ginormous and the aha moment ensued. British & American terms for crochet stitches are not all equal. And I was using a British pattern with my Midwest American knowledge.
All this experience comes in handy when a customer calls up with a slight panic in their voice. After a jog of my withering memory, I recall the customer and the project in question. It was to be a wild crocheted baby hat for a photo op. The pattern to be used looked like it had been around for a couple decades and the yarn used was elusive. So, we took a small chance on a substitute yarn. Small because I had an educated hunch it would work. The minute she said the piece turned out way too tall, I asked about the pattern's publication location. She scoured the copy to find out that indeed it had been published in Britain. Per my instruction, crocheted conversions from British to American were googled and obtained. Rework occurred, and I received this way too funny picture of the successful outcome. I love a challenge.
Here is a handy link to a conversion chart.