Currently we have a tag for "Fantastic Beasts" fantastic-beasts whose wiki reads:
Use this tag to refer to the fictional book called 'Fantastic Beasts and Where To Find Them', the 2016 film of the same name, or the five-movie franchise it began. Use this tag with the [harry-potter] tag.
I find this very confusing and not fitting with our tagging conventions (especially when it comes to new works and ignoring tags due to spoilers).
Therefore I propose that we split the original book and film into two separate tags. I see two pretty straight forward options, which I have added as answers below.
I have added my two options to be voted on accordingly. Feel free to add other options if you have a different idea.
I prefer option 2 as it gives a greater level of clarity with 5 films coming out that will share the "Fantastic Beasts" prefix.