Sonic the Hedgehog: The Invisible Robotnik

Sonic the Hedgehog: The Invisible Robotnik is a picture book published in the UK by Ladybird Books. It was released alongside Sonic the Hedgehog: Robotnik's Oil, and both feature fold-out center pages. The story takes place in Sonic the Hedgehog 2's Hill Top Zone.

Plot
Dr. Ivo Robotnik believes he has finally come up with a plan to eliminate Sonic: he has built an invisibility machine in the Hill Top Zone. He immediately uses the machine on himself and is successfully turned invisible. Soon, Tails and some of Sonic's animal friends see Robotnik's flying vehicle coming toward them, but as it comes closer, discover that is flying without a pilot, and run away in fear.

Later, Sonic is running through the Hill Top Zone collecting rings, unaware that an invisible Robotnik awaits him. However, an oblivious Sonic runs straight over Robotnik's toes at supersonic speed. After tending to his injured feet, he vows to get even with Sonic, and is next not seen hiding atop a loop. As Sonic runs through it, Robotnik tries to grab hold of him, but misses, landing on a group of passing Spiker badniks, freeing several animals.

Having failed twice, Robotnik decides to take a rest and heads for one of the zone's trams in order to move to a lower level to plot some more, when Sonic jumps onto the very tram he has just boarded. But once again, Sonic is too fast for him, and impatiently jumps away just as Robotnik tries to grab him, causing him to fall into the water below. He soon makes known his plan to bring a life jacket on his next expedition.

Swimming to shore, Robotnik scares some more of Sonic's animal friends when they see nothing but mysterious splashing, cheering up the glum villain. Still not having given up, Robotnik hides near a spring, but before using it, Sonic changes his mind and uses a see-saw instead. Trying to catch up, Robotnik jumps on the spring himself, but crashes back to earth directly in Sonic's path, and is summarily run over yet again, after which several badniks belatedly attack, unknowingly hitting their master instead.

Robotnik finally grows tired of being invisible, and returns to his machine to reverse the process, after which he deliberately overloads it to avoid a recurrence of the disaster. But just as he begins celebrating the destruction of his machine, Sonic appears, knocking him off his feet as he runs by. Sonic facetiously apologises, claiming that he hadn't seen Robotnik, before running off into the distance.