The Giant Reptilian Bird is the hypothetical creation of foster care parents Mr. and Mrs. Weatherhead. Their rules of agnosticism state, "We cannot know for certain if God or Christ existed. They could. Then again there could be a giant reptilian bird in charge of everything. Can we be certain there isn't? No, so it's pointless to talk about."
This creature ironically turns out to be real. After breaking through South Park Elementary's roof, it attacks Kenny McCormick, violently bashing him against the walls before eating him whole, and then leaves.
- The Giant Reptilian Bird is similar to a now extinct species called Gastornis, a flightless bird that existed during the Cenozoic era.