Sega and Nintendo may be firm friends these days, but once upon a time they were the bitterest of enemies, fighting tooth and nail for dominance of the burgeoning home console market. In the 8-bit era it was the NES which achieved the most success globally, but Sega's rival Master System - with its monkey-boy mascot Alex Kidd - did its best to upset the order of things with faithful arcade ports and superb exclusives.
Before the battle between Sega and Nintendo reached its boiling point in the early '90s, it would seem that the former wasn't above the idea of lampooning the latter in its video games. In Alex Kidd in Shinobi World, one of the end-of-level bosses was actually based on Mario himself; in a prototype version of the game he has a moustache and is called "Mari-Oh", a reference to Ken-Oh, the first boss in the original Shinobi.
Shinobi World began life as a parody of Shinobi, and didn't actually feature Alex Kidd until it was close to completion; clearly, Sega felt that adding its mascot would bolster the fortunes of the title. It also had a slight change of heart regarding Mari-Oh - in the final release, the boss is called Kabuto, but he still throws bouncing fireballs (like Mario once he's consumed a Fire Flower) and, when he takes a certain amount of damage, he shrinks - just like Mario when he's hit after eating a mushroom.
You can see Mari - sorry, Kabuto - in action below (skip to the 3:49 mark to see him).
Of course, many years later Mario would star in a Sega game - Mario & Sonic at the Olympic Games - and Sonic himself has gone on to feature in the Smash Bros. series. Times have changed, but if you're old enough to recall the rivalry between these two companies, then knowing that Sega almost put Mario in one of its 8-bit releases should raise a smile.
Can you recall any other instances where developers have subtly (or not so subtly) lampooned other characters in their games? Share your favourite examples by posting a comment below.