When thinking about setting my game inside a human, and now a dinosaur, I suddenly remembered that this has been done (and done well may I add) in the TV series Adventure Time. The episode Belly of the Beast, and a personal favourite at that, is based around a group of bears who have adopted a monster's belly as their cave and proceed to party in there oblivious to the situation they're in. This comic episode is cleverly explored and isn't like the stereotypical 'travelling into someones insides' style films/animations that have been done before. The environment design has been kept very simple and basic, with little colour change and texturing, yet it is still recognisable as the insides of a being. The fact that the monster's belly is filled with small cute bears also removes the viewer from the otherwise disgusting setting, allowing you to focus on the story more. Within my game, I wish to use this method, by filling the environment itself with well designed and charming assets, allowing it to fit under the 'Joy' them better.
Below is the full episode if you would like to look into further detail, and below that are a few screengrabs on the environment which I have been most influenced by.