Earlier quoted context omitted.
If I have a library, I must be a player. In that case, how do I get -5/-5? Players don't have P/T.
Form of the Dragon begs to differ... /s
But, a life total is a unique characteristic of players, not creatures, and it's not P/T, while the ability to directly damage a creature or player is distinctly different from the ability to _attack_ a player (and enter combat with a blocking creature). So no, Form of the Dragon doesn't make you into a creature.
I suppose a card that actually turned the player into a creature, now that would be a fun card and I guess it could be done without even a token to represent the creature since you have the person's own body as a physical representation. You could get vigilance to avoid having to tap, because that would be awkward. Some people might misunderstand the ability of a creature to "attack" an opponent and that might cause some trouble. Anyway, probably a card for an un-set.
/p
(for pedantry).