Plot hole: It takes less than 3 minutes to fill the house with water using a mere garden hose? I mean come on...
Plot hole: Before giving his father's piece of string to his brother, Lars kept it in his suit's pocket, however in a scene in the factory, we see that Lars' suit gets entirely destroyed and yet later on in the film, he somehow has the string.
Answer: It survived because it's funny. Just like it survived everything else the brothers tried to do to it.
Grumpy Scot