Presumably the 'fire' group has something to do with Pokemon?

"Onix" should be spelled onyx - I thought the spelling was a red herring and so was avoiding putting it in the rock group. Not sure what "one trick" means either. Not many clues that can fit into multiple groups either. Hopefully your next grid will be better.

Fire group made no sense at all to me. Must be niche, as suggested already.

It`s a Fire Pokemon-fooled me too tho` I got Pokemon (not good enough apparently) . Trick set is a bit meh! but I`ve heard of one trick means someone who can only do one thing-one hit wonder pop star for egs. Onyx-I`d `ve got it more easily if it had been spelled right. And who are all those Johnsons? 🤣 Never heard of ONE. ANY cross overs?