Watch for the scene where Garp is wrestling and keeps watching Jenny. The referee is John Irving, the author of the novel on which the movie is based.
While Helen and Garp are house-hunting with the real-estate lady, a small plane crashes into the 2nd story of the house, "predisastering" the house for the couple. The pilot is in fact John Irving, the author of the novel.
(I'm not sure if this scene... more