Gandalf's powers

[Boromir88]

Can Gandalf really turn people into other things?~Melilot

No, he can't, but Sam doesn't know he cant; and that's the important thing.

Also, I think there was a bit of confusion as it was Frodo who told Sam if he didn't keep quiet then he hopes Gandalf would turn him into a toad. But Frodo knew Gandalf would not harm Sam, yet again, what's important is that Sam doesn't know that.