The idea of Barney interacting with the magical creatures in Harry Potter is also quite fascinating. Imagine him trying to outwit a hippogriff or make a deal with a house - elf. And then there's the aspect of him trying to blend in with the wizarding society. He would have to learn about magic, and his misadventures in doing so could be really hilarious. For instance, he might accidentally turn himself into a teacup instead of a proper wizard's robes when trying to use a Transfiguration spell.
A really interesting concept could be Barney's take on the different houses in Hogwarts. He might try to form his own 'house' based on his own values of confidence and self - promotion. Or he could be sorted into one of the existing houses and cause chaos within it. He could introduce his own set of rules and traditions that would completely disrupt the normal Hogwarts life. Also, his reaction to the Forbidden Forest and all the dangerous things in it would be quite a sight to behold.
One interesting concept is Barney's attempts to use his playbook in the wizarding world. For example, his pick - up lines might be adapted to suit the magical context, like 'Is that a wand in your pocket or are you just happy to see me?' Another concept could be Barney getting involved in Quidditch. He might try to use his charm to become a team mascot or something.