During the Any Old Iron number, one of the Muppet Whatnots in the background is missing the pupil in his left eye.
Right before Elton John miserably finishes singing Crocodile Rock after falling into the pond of crocodiles, a puppeteer's head is visible behind the leftmost crocodile in the shot.
While Elton John is singing "Goodbye Yellow Brick Road", stage lights can be seen in the reflection of his sunglasses.