Poehler previously had a supporting part in the ice skating comedy Blades of Glory, and a cameo in the reporter battle sequence at the end of Anchorman 2: The Legend Continues, but she never shared significant on-screen time together with Ferrell before The House.
More seriously, Will Ferrell and Amy Poehler have been in the comedy game for roughly the same amount of time, but their careers weirdly only have limited crossover.
(You’d think that they could have come together for an episode of Parks and Recreation, but it never happened).
They came up through different theaters (Groundlings vs UCB), and Poehler joined the cast of Saturday Night Live the year that wound up being Ferrell’s last (2001).