Which fictional character would you most like to see diapered/would you most like to care for?
In my case, it would be Sherlock Holmes from BBC Sherlock. There is a small but fabulous collection of AB/DL fics on AO3.
Many of these fics illustrate Sherlock as being neglectful of his own needs (including bodily functions, bathing, sleeping, etc.) or in needing a break from the pressures of his brilliant mind and challenging work.