I believe that's a parasite that has attacked the mushroom. If you happen to see a mushroom that looks like it stuck its finger in a light socket you're probably seeing something rarely seen.

Called a 'mycoparasitic mucorale,' Syzygites megalocarpes pin mold has been found on about 65 different mushrooms, but it will only appear when the temperature and humidity are absolutely what it considers perfect. It has multi branched sporangiophores that make the mushrooms it attacks look like it is having a bad hair day. This pin mold can appear overnight. Great picture! You timed that one perfectly :-)