I recall one afternoon I took mushrooms, when I was perhaps 15 years old. Not a huge quantity, but enough for a mild, pleasant experience.
That same evening I realised that I had to write an essay for school - it wasn't like me, but I'd completely forgotten about it, and now had a single evening to write a whole essay... bah, how could I possibly do that?!
I sat down, and... it just flowed. Words, sentences, paragraphs, ideas, characters, just sprang to life on the page - and it was good, really good! My mind felt amazing - like my consciousness had been expanded. I'd never felt such pure imagination and joy of knowledge before.
By the end of the evening I had unquestionably the best essay I'd ever written, and about twice the target length.
A week or so later when I got the results, it was a B, and I was kind of shocked. But the teacher called me back after class - he told me what I submitted was way better than A+ work, more what would be expected at university level. He also asked who wrote it, because "it obviously wasn't you" - he didn't believe my insistence that I'd written it. He couldn't prove anything, so gave it a B and strongly warned me not to "pull a stunt like this ever again".
Of course, people can have great ideas and do great work without hallucinogenic drugs - that should really go without saying. But the results with such drugs can be utterly incredible - Also keep in mind the effect is not only while using the drug, but afterwards too.