In the Pokemon Adventures manga, Koga used some kind of item (like a syringe) on his Rhyhorn:
The strange part is that the Rhyhorn suddenly evolved into a Rhydon, in the middle of the fight:
Red confirmed this:
I didn't understand how it would be possible to make Rhyhorn to evolve like this, because Rhyhorn is not the kind of Pokemon that could be evolved by stones.
So what did Team rocket use? Does this item appear again in the manga and did someone explain it better? Or does it even exist in the TV series?