Comic mega star Will Ferrell has pledged to go skinny dipping in the Liffey during his visit to Dublin.

No stranger to Ireland, the Anchorman 2 star said he expected about 50 people to turn up to the movie's premiere.

But he was astounded to see hundreds lining the pavement of the capital's main thoroughfare O'Connell Street tonight, craning to catch a glimpse.

"It's been fantastic," he said, as he headed into the packed Savoy Cinema to introduce the eagerly-awaited comedy sequel.

The star, 46, and the rest of the film cast sampled some of the capital's best Guinness at popular pub Toner's before the premiere.

"I just had a half pint," he insisted.

Ferrell, who is best known for his role as anchorman Ron Burgundy in the blockbuster films about San Diego's top news team, said it was great to reprise the part.

"We obviously had a great time being back together and recreating, bringing those characters back to life," he said.

The star, whose family has connections with Longford and who was awarded the prestigious James Joyce Award at University College Dublin five years ago, seemed undaunted by the cold December chill when he insisted he was going to jump in the Liffey "in the buff".

"Right about 1am in the morning, if you have the courage to do it, join us," he added.

Ferrell, also known for his hilarious role in Zoolander and his earlier TV sketches on Saturday Night Live, walked the red carpet with his fellow cast members Paul Rudd and Steve Carell.

Rudd, who plays man-on-the-street reporter Brian Fantana in the Anchorman films, joked the Irish authorities would not allow him to bring his character's potent Sex Panther Cologne into the country.

"It has been outlawed by most governments," said Rudd, who also starred in hit TV show Friends.

"It really is probably for the safety of most citizens."

Unlike Ferrell, who has been a frequent visitor to Ireland, star of The Office Carell revealed this was his first time on the Emerald Isle.

"We've been here about 10 hours, it's the first time I've ever been to Ireland and so far so lovely," he said. "People have been really nice."

The star, who plays "I love lamp" weatherman Brick Tamland, also revealed that the cast would consider reuniting for a third Anchorman film.

"We'll see how this one goes," Carell said. "If people like it, maybe 10 years from now we'll do a third."

The stars also refused to rule out returning to Ireland for future movies.

In 2008, Ferrell was honoured for his tremendous contribution to comedy and entertainment - with the UCD James Joyce award in the same way as United Nations weapons inspector Hans Blix and former South African President FW de Clerk.

Ferrell accepted the award at the time dressed in a full Irish rugby kit.

Anchorman 2 opens in cinemas across Ireland on December 18.