Thank you for your question.
The First Amendment allows you to poke fun at public figures such as W. He can sue but as long as you do not make false assertions of untrue facts he would not win such a case.
Even a false assertion of an untrue fact may be protected if it was clearly a satire, see HUSTLER MAGAZINE v. FALWELL in which
Respondent, a nationally known minister and commentator on politics and public affairs, filed a diversity action in Federal District Court against petitioners, a nationally circulated magazine and its publisher, to recover damages for, inter alia, libel and intentional infliction of emotional distress arising from the publication of an advertisement "parody" which, among other things, portrayed respondent as having engaged in a drunken incestuous rendezvous with his mother in an outhouse.
The Supreme Court held:
In order to protect the free flow of ideas and opinions on matters of public interest and concern, the First and Fourteenth Amendments prohibit public figures and public officials from recovering damages for the tort of intentional infliction of emotional distress by reason of the publication of a caricature such as the ad parody at issue without showing in addition that the publication contains a false statement of fact which was made with "actual malice," i. e., with knowledge that the statement was false or with reckless disregard as to whether or not it was true. The State's interest in protecting public figures from emotional distress is not sufficient to deny First Amendment protection to speech that is patently offensive and is intended to inflict emotional injury when that speech could not reasonably have been interpreted as stating actual facts about the public figure involved.
I hope this information is helpful.