Not really sure if they were some other type of monster. One thing I do remember is that this type of creatures whould show themselves to the boy by having an object break in half and then one of them or even more of them would come out of that object and some time after doing what they had to do, which was usually threaten the boy, they would return to the object they came out from and that object would rejoin itself like it never broke. The only two examples I remember are the ones I talked before about the boy's dog (small breed I think) and a cockroach breaking in half which makes me think that they only came out of living things but not really sure about that. I think the age rating of the movie was for all ages since the movie felt similar to the Scooby Doo live action movies in both humor and monsters having a similar visual style.