So, in "Asterix and the Big Fight" there's this Roman legionary who is forced to spy on the Gauls. Of course, he gets captured, and then he is used as a guinea pig to test potions brewed by the druid Getafix, who has lost his memory and doesn't remember the recipe for the super-strength potion. The first potion makes the poor Roman spew fire (which hurts his throat and makes him cry...) and grow a reptilian tail.
Oneday I found two reviews on this cartoon (based on two different English dubs) on YouTube, and in one of them the author points out how after the Roman became part-dragon, Getafix (seemingly) didn't add anything new to the potion before giving him a second dose, and how logically a double dose of the same potion should've fully turned the Roman into a dragon.
That's pretty much how I got the idea to draw this...

NOTE: this image uses my DeviantArt/Inkbunny/Tumblr signature