Minor Pet Not Eating?

Mods run entirely in the game environment, meaning they load up into memory (RAM) as the rest of the game does. Tuning mods adjust the way functions that are already in the game work, Script and Core Mods add new functions or replace existing functions with different code. It is true that badly made mods, those strictly for earlier patch levels, or those that conflict with each other may cause the game to fail on startup or things to not go as one would hope, but they are not going to break anyone's computer.

Most mods are easily removable if they do not work out, some are a little trickier or come with a removal procedure, and there's a small number of them out there that are so intrusive that if one removes them one has to start a new game. But none of them affect the game program install or the operation of the computer when the game is not being played.

Afraid I don't know why your lizard is not eating nor seeming to get hungry, but honestly I don't find feeding small pets to be any more fun than having to clean their cages and would probably have my sims use the time they have saved by playing with their critters more often. :)