Help me find a funny campaign about dragons (description inside).

Basically, it starts with a hero and a single peasant in their army. I remember on one of the maps, there was a puzzle – a 4x4 field of cells with different types of soil, and you had to arrange them into 4 rows to reach the artifact. On this map, instead of a peasant, the hero travels with a dragon, who constantly makes all sorts of jokes.
Anyway, it's funny, unconventional, and I liked it. What's it called, and which part is it from?

P.S. What are the differences between Heroes 3 and Heroes 3.5?