Huh?

What is a gatito parvulo? The words are spoken by a character in Josh Lanyon and Laura Bambach's Mexican Heat. The speaker is Spanish, but is undercover as a Mexican drug lord. [Which begs the question -- did they think about the fact that the two are not interchangeable?] Anyway, the only definition I could find of 'parvulo' was 'nursery school'. Does it have some other colloquial meaning that I'm missing? Because that really doesn't make sense as a nickname (to me). Of course, some of the other Spanish used didn't make much sense either. Ex: mi amigo grande del amor (my big friend of love?) and 'comprender', when asking "understood", which probably ought to be 'comprendes'.

Another question: are madre dios and madre mios colloquialisms or exceptions to the gender/number rule? I would think madre mia, and madre de dios would be grammatically correct. No?

ETA: okay, I found two other definitions: 1) de corta edad; or 2) inocente o ignorante. Well, the last isn't flattering and wouldn't work so much as an endearment, but since the speaker was referring to a younger man, the first definition could apply. It still doesn't work for me -- in part because, hello, accent needed over the a, and also because the spelling makes me think of parvo, a viral disease that can kill dogs.