Pleasing a toddler isn't always easy, but I have an approach to suggest. It worked for my nephew and might for you as well (depending on your child's temperament). The idea is to include them in the process and ask them to choose what they want. That way, you know they at least like it at that exact moment. To combat the issue of an ever-changing mind, I suggest waiting until reasonably close to the party to give them a choice. That leads me to the second suggestion. You can make it easier by buying or making some supplies ahead of time. Then much closer to the party, allow your child to pick one or two things for the party (preferably the things that don't require lead time). That way, there is a smaller time window for them to change their minds. All that said, there is a way to tell if it is a reasonable bet. If they've loved Bluey for months/years, that is probably the safest bet you can make.