If a cartoon draws a likeness to a celebrity and actually uses that celebrity's name, can the cartoon creators be sued by the celebrity?

Not in the US, freedom of the press and freedom of speech protects people to make cartoons of whoever they wish.

Larry Flynt, publisher of Hustler magazine, was sued by Jerry Falwell, a religious leader, for a parody of Falwell having sex with his mother. It went all the way to the supreme court and in a 8-0 decision, Flynt won under the 1st amemdment.
https://en.wikipedia.org/wiki/Hustler_Magazine_v._Falwell

ANYONE can be sued for ANYTHING in the USA. It is a question of winning that the laws support or dismiss.

And yes defamation of character does weigh on this scenario.

Many celebrities have sued tabloids and won for unbecoming stories about them.

Many celebrities have stopped stories from running by the hand of the court.

I. What Is Defamation?

California law defines "defamation" as either "libel" or "slander".

Libel involves statements expressed in writing, picture or fixedrepresentation. Pursuant
to statute (California Civil Code Section 46):

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Slander is a false and unprivileged publication, orally uttered, andalso communications by radio or any mechanical or other means which:

1.Charges any person with crime, or with having been indicted,convicted, or punished for crime;

2.Imputes in him the present existence of an infectious, contagious, or loathsome disease;

3.Tends directly to injure him in respect to his office, profession,trade or business, either by imputing to him general disqualification in those respects which the office or other occupation peculiarly requires, or by imputing something with reference to his office, profession, trade, or business that has a natural tendency to lessen its profits;

4.Imputes to him impotence or a want of chasity; or

5.Which, by natural consequence, causes actual damage.




http://answers.google.com/answers/threadview?id=244096


http://answers.google.com/answers/threadview?id=244096

In the cartoon "South Park", Trey Parker and Matt Stone frequently use likenesses of celebrities with their actual names portrayed in a very unflattering light doing things they couldn't possibly have done.

However, they escape lawsuits because parody and satire in the US fall under a category called "Fair use".
https://www.cotmanip.com/articles/fair-use-parody