The unarmed 17-year-old African-American was shot to death by Florida neighbourhood watchman George Zimmerman late last month. Allegations have been made that race played a role in the killing, but Zimmerman told police he was simply defending himself.
Zimmerman has so far not been charged with any crime in relation to Martin's death.
A person who goes by the username 'RealWillFerrell' on Twitter posted a tribute to Martin over the weekend and attempted to launch what appeared to be a legitimate fundraising drive.
"R.I.P. Trayvon Martin… For every R-T this tweet gets, $1 will be donated to the #TrayvonMartin Foundation, which helps counteract racism," 'RealWillFerrell' tweeted.
Ferrell's spokesperson has now denied that the tweet was legitimately written by the actor.
"That is definitely NOT Will Ferrell who does NOT have a Twitter account. We've informed Twitter that this is a hoax," the actor's rep told The Hollywood Reporter.
The fake pledge had been retweeted hundreds of times before it was deleted by Twitter. Parks and Recreation star Aziz Ansari initially fell for the hoax, but later tweeted: "just realised it was fake, just read it and it seemed legit. F**king fake Twitter people. Ugh."
Spike Lee, Reverend Al Sharpton and Diddy have all called for Zimmerman's arrest in the month since the killing took place.
Sinead O'Connor penned an open letter to Martin's family on Monday (March 26) to personally offer her condolences and call for an end to racial injustice.
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Watch Reverend Al Sharpton speak at last week's Trayvon Martin rally below: