Sentence:  For Ralph, any encouragement is too much. When Lisa gives Ralph a valentine bearing that locomotive pun that so affected "The Simpsons''' showrunner, Ralph misinterprets the gesture as a genuine display of romantic interest rather than a gesture of pity from a thoughtful young geek to a friendless <WSD>goober</WSD>. 
Meaning of the word marked with <WSD> tags:  A foolish, simple, or amusingly silly person.