I’ve heared of strange objects, like fish, being found inside logs of wood or rocks. I did a google search, but couldn’t find anything. What gives? 
Are you asking about fossils or what?
Nah, X-Files stuff:
I have seen basswood, but I’m pretty sure it didn’t have fish in it. 
No, not fossils. The fish was apparently alive inside the wood. Something similar to Desmostylus frog link.
Most of these objects seem to have been discovered in the Victorian era or before; I’m going to boldly suggest that they consist of:
-A rather small number of genuine cases where (for example) a frog crawled into a crack in a rock (or squeezed into a hollow log) and later appeared to emerge from a completely enclosed cavity.
-A slightly larger number of genuine cases where an animal happened upon the scene at the moment when an object containing a sealed cavity was being broken open (and perhaps had fallen to the ground) - hasty conclusions along the lines of: unusual cavity+unexpected animal=animal must have been in cavity, right?
-A significant majority of hoaxes, some of them based on manufactured evidence, others based on nothing more than fanciful writings.
FTR it used to be common for miraculous things to “discovered” in coal, such live animals, modern technological items (such as spark plugs) and human-carved figurines. A book I inherited at home has photographs of things even as ludicrous as a carved replica of the Venus de Milo, complete with missing arms, found in a piece of coal about 300 feet underground. In West Virginia. Some of these items are “cited” as “proof” of either a Biblical time scale, ET intervention, Atlantis, or that people just like pulling off hoaxes.