Fortunately, the Milk (2001)

A little boy and his little sister awake one morning, milkless. Their mother is away on business, their father is buried in the paper, and their Toastios are dry. What are young siblings to do? They impress upon their father that his tea is also without milk and sit back to watch their plan take effect. But something goes amiss, and their father doesn’t return and doesn’t return some more. When he does, finally, he has a story to tell, a story involving aliens; pirates; ponies; wumpires (not the handsome, brooding kind); and a stegosaurus professor who pilots a Floaty-Ball-Person-Carrier (which looks suspiciously like a hot-air balloon). There is time travel, treachery, and ample adventure, and, fortunately, the milk he has procured is rescued at every turn.