what is the difference between a soprano d whistle and
soprano d flat whistle?
One of them has been stepped on.
No, half-stepped on. The difference is a half-step.
Does it always have to be about dancing, for you?
d flat?
Isn’t that what Herve Villechaize called his apartment in London while he was playing the little guy “Tattoo” on Fantasy](http://www.tvtome.com/images/shows/0/6/79-8879.jpg%22%3EFantasy) Island?
Well, since nobody has given you a real answer yet I will 
First, where did you hear of a D flat whistle? I don’t know of any makers making Db (D flat) whistles, and musically if they were I would think they’d probably be called C# (C sharp) just 'cause that’s the more common name for the note the way scales work out.
In any case, the bell note (all holes plugged) of a D whistle is, surprise, D. The bell note of a Db whistle would be Db (or C#, if you prefer).
A Db whistle would probably be of limited usefulness because there just aren’t that many songs, especially trad songs, in that key or in the “second” key, which would be F# on a Db whistle. There are a fair number of hymns and such in Ab, the “third key” of a Db whistle.
Finally, lest you think I’m entirely too serious, you can see another kind of Db whistle in my Avatar…
There are Db Cheiftain whistles advertised at Lark in the Morning. I believe it is a typo and should read Bb…But I don’t for certain.
Phil Hardy had one for sale: http://chiffboard.mati.ca/viewtopic.php?t=28235
But I don’t know if it’s still available
What were his favourite flavour of potato crisps (chips)?
Altogether now - THE PLANE! THE PLANE!
Sorry,couldn’t resist that!
Seriously- Db/C# whistles are made by John Sindt-I have a C# tube on order.
Not only will it complete my Sindt set,but will allow me to play along with Seamus Ennis’s C# Pipe recordings,and,as someone interestingly mentioned recently,it will allow playing ‘Baroque’ music at A= 415 (taking half holing into account).
Wow! Someone understood my obscure reference.
But I think it was “D-plane, d-plane boss.” 
No it was Duh Plane; Duh Plane.