Mark Acheson, who appears in the mail room scene of the Christmas classic, tells PEOPLE about improvising with Will Ferrell

Will Ferrell and his brother Patrick Ferrell enjoyed sharing funny moments when they were kids

"It's really quite special," the actor tells PEOPLE of the beloved holiday film, which was released in 2003

The actor starred as a cast member on the late-night comedy sketch series from 1995 to 2002

The pair — who share three children — have been married for over two decades