Can horses walk on their hind legs?

For very short periods, but it's not really a natural thing for them to do. However, an Arabian horse called Desert Kismet holds the Guinness Record for "Fastest 10m on hind legs by a horse" (9.21 seconds). Teaching a horse to do this requires teaching them unnatural coordination and muscle development. The typical horse can't even stay on their hind legs for that long at a stretch - physically can't. They aren't made to do it.

Here's a video of Desert Kismet doing his signature trick.