The correct answer is Walt Disney, but tangentially. The Mickey Mouse watch famously used Mickey's hands as clock hands, which seems to be the earliest example I can find of using Mickey's hand as a pointer:
Image source unknown
As far as I can tell, the pointing hand cursor originated as a PC cursor in HyperCard as mentioned in Bart's answer, and was adopted for use on the web pretty much right from the beginning as noted by Mark Griffiths:
HyperCard was a big influence on some of Tim Berners-Lee’s team at Cern, and many of the hypermedia conventions it established were carried through into Mosaic.
I'm struggling to corroborate that claim. He goes on to say:
Had the pointing-hand cursor never existed then a whole bunch of design assumptions might not have been transferred from HyperCard’s ‘link’ to HTML’s and we might have preempted the many years of work done to sort out web accessibility for machines and the full spectrum of human beings.
The open/grabbing hand cursor, though, is much older, and was designed by Susan Kare (who did most of the icons for the original Mac). MacPaint (on the original 1984 Macintosh) used it as the "pan" icon:
That icon was tweaked slightly over the course of classic System/MacOS to add things like a countdown waiting animation:
Image credit: Bjørn Sortland, Ka of Isis
Old point-and-click adventure games also used hand icons quite a lot, often richly-designed gloved ones, which starts to hint at that direction. Final Fantasy is a famous example. It would seem likely to me that there's an old point-and-click adventure game somewhere—possibly even a Mickey Mouse themed one—that used a cartoon glove like this well before it became part of the OS, but I couldn't find any explicit examples (it's not a genre I am particularly knowledgeable about).
As far as I can tell, it was the pointer icon that first got the Mickey Mouse darts in the back on a computer, which happened on the Macintosh system software some time before Mac OS 9 (sadly I can't seem to find a more specific example than this, but it wouldn't have been much before that since the pointing icon was only made a system icon in Mac OS 8.5. That coincides with the launch of the Platinum UI in Mac OS 8.5, which was all about richer bitmap graphics throughout the OS):
Image credit: Nonme85851, DeviantART
The icons were brought into line at some point, but it's not clear when:
Image credit: Offscreen Graphics Worlds, Pictures, Cursors, and Icons Chapter 13 (PDF link)
It seems that the stylised hand icon was reverted to the original Susan Kare version in OS X all the way until Mac OS X 10.7.3 (when the two cursors were redrawn for Retina displays and brought into line stylistically):
Image credit: Marc Edwards, Twitter
I had a look at the metadata for those cursors in OS X and they don't seem to have any author credit specified (but it does say they were being worked on in Adobe Illustrator CS4 from the 17th of April 2008 at least until the 15th of September, 2011).