The Disney EverNotice site was a favourite of mine in my younger days, until it shut down. Fortunately, with the help of the wayback machine at archive.org, it is (sometimes) able to be seen again. And thanks to Paul Reiter providing a link over on A.FilmL.A., I was able to re-read an odd theory that was put forward on that site.
Visit the EverNotice Snow White page here, and scroll down the post by "Polar Bear" which begins "I've not seen the movie in a few years..." Basically, what the post says is that the character of Sleepy was a last-minute replacement for a different character, and that the evidence to support this is that Sleepy only appears for "a few minutes".
The strangest part of the theory is this: "Polar Bear" identifies another dwarf who appears in most scenes, with "a hatchet face and a red vest" who gets the lines "Goldenrods!" "Do you have to wash where it doesn't show?" and "Was it hard to do?" (in the lead-up to Someday My Prince Will Come).
The implication is that this other dwarf (with at least three lines of dialogue!) is a mysterious un-named character who appears in most scenes *in place* of Sleepy, but that's not really borne out by the film: the description matches Grumpy, Bashful says "Goldenrods" and "Do you have to wash..." and Sneezy (surprisingly, not Sleepy himself) asks "Was it hard to do?"
Incidentally (or not), Michael Barrier says the last dwarf name to be chosen was Sneezy, but that for a few days they were still considering "Deafy" instead. This was before animation began though. Still, you do have to wonder though: Sleepy and Bashful can look almost identical except for the facial expressions, there's a point at the beginning of the "Spooks" sequence where Sneezy seems to turn into Sleepy (scenes 5 and 7 on the draft), and scene 14, described in the draft of the "Entertainment" sequence as "Happy and Doc push Bashful forward" actually has Doc and Sneezy. One wonders if there were any points where one dwarf was redrawn as another...