To be a Toby means to disappear and then reappear whenever you
desire getting anyone who is looking after you into
trouble. This word is used in the curious incident of the dog in the night
time, as Toby the rat gets the main character in trouble a lot.
Don’t be such a Toby. -As Toby is meaning to
get others in trouble, this sentence is referring to the
person who is being a toby getting someone else in trouble.