If I remember correctly, the game name contains the word "Old" but I don't remember the farmer's name and it's most likely not McDonald as I couldn't find it.
There is an opening cutscene that shows a cow with just a head remaining and bleeding, which prompts the farmer to take revenge on the ones that (supposedly?) killed his cow.
And if my memory serves me right, brown rats are a type of enemy, and one of the weapons is a taser which comically causes the enemy to shock like an idiot without causing damage.