The pair's roles in the upcoming sequel are currently unspecified, Deadline reports.
Lawson has previously appeared with Ferrell in The Campaign.
Steve Carell clarified earlier this week that Meryl Streep will not be in Anchorman 2, after previously seeming to suggest that she had asked him for a role.
The movie has, however, cast Harrison Ford in a supporting role, while Kristen Wiig, Dylan Baker and Meagan Good have also joined the ensemble.
Photo gallery - Anchorman's 20 greatest quotes:
Copyright: DreamWorks Pictures / Apatow ProductionsWill Ferrell, Paul Rudd, Christina Applegate, David Koechner and Carell are among the returning Anchorman cast members.
Ron Burgundy will be making a special appearance for the UK's Comic Relief: Funny for Money show tonight (March 15).
Anchorman: The Legend Continues will be released on December 20.
Watch Paul Rudd and Judd Apatow speak to Digital Spy about the film below: