A ruler.
or
Two… one to tell the engineer to do it, the other to say "I don't know, what do you think?"
or
What's up, dock?
or
Because she wanted to get a good scoop.
or
Because an undocumented worker has been living on his head for the past 2 decades!
or
None: they just deny that the bulb ever went out in the first place.
or
Three skunks fighting over a pickle
First dog: My master calls me Furball. How about you?
Second Dog: My master calls me Sitboy
or