When Spencer is talking about "Mr. Schneider and Mr. Newman", he is referencing Dan Schneider, the Executive Producer of iCarly and Andrew Newman, a writer for some iCarly episodes.
This episode is a loose adaptation of "It's a Wonderful Life." Carly makes a wish that her brother was born "normal" and an angel sent down to help show her how her life would have been if Spencer were born without his quirkiness. In It's a Wonderful Life, the character George wishes he never been born and experiences what life would look like had he not come into existence. It also reference The Twilight Zone Person or Persons Unknown (1962).
This episode only airs during Christmas.