In the first scene with Harry, Sally, Tommy and Dick, the scanner on the table switches from standing to lying on its side multiple times.
When Dick and Mary have just finished go-carting, Mary takes off her helmet. The studio lights can be seen reflected in it, although the scene is set outside.
When Dick walks into the faculty luncheon wearing his blue bathrobe, there is a clear, and quite complete, shadow of a boom mic on his back.