M'Bu is the assistant to wildlife stock trader N'choate. Twelve years old, dark skinned and with teeth sharpened to points (because his tribe like the look of it), he can easily count elephants, especially when you only have three.
His boss thinks of him as merely a 'mobile smile', so when an order comes in for a thousand elephants (during the events of Moving Pictures), Azhural is surprised to find that the kid has the mind of a skilled kilopachydermatologist. Together they wrangle in several relatives and scores of elephants, and trek over a thousand miles across mountains, through forests and across ravines.
Unfortunately this great adventure was ultimately for naught; the elephants were no longer needed (and could no longer be paid for) by the time they arrived at Ankh-Morpork. Nothing is said of what happened next, but it is almost certain that the elephants had to be marched all the way back home again, and no compensation was given.
Hannibal was the Roundworld guy who liked to force elephants into as many battleplans as he could. He even took elephants over mountain ranges, although he didn't use giant sleds.