At least some of his cameos were down to Trump demanding them in return for the use of locations he owned.

E.g. that's the case for Home Alone 2, where he demanded the cameo for the use of The Plaza Hotel:

https://www.mirror.co.uk/3am/us-celebrity-news/real-reason-d...

I dont remember how much it carried over to the film but in the book, Trump is the person the titular psycho...

> idolizes above all others. Bateman talks about him constantly, citing incredibly specific details of his life of luxury, and is often distracted by the thought of seeing Trump or his wife Ivana out in New York City.

I can top that. As a child I was a fan of a relatively unknown sitcom titled “Out Of This World” and I rediscovered it a couple years ago. It was truly surreal to hear Donald Trump mentioned in a show from 1987–1991. (American Psycho is from 2000.)

The novel is from 1991.

Trump was the prototypical 1980s rich person. E.g. see Roger Ebert's Wall Street review:

https://www.rogerebert.com/reviews/wall-street-1987