Ehasz began his writing career in the year 2000, working as a staff writer on Ed and on Mission Hill. In 2001 he took a position as story editor on Matt Groening's animated Fox series Futurama, where he worked until its cancellation in 2003. From 2005 until 2008 he served as a co-executive producer and head writer for the acclaimed Nickelodeon series Avatar: The Last Airbender. When Futurama was revived by Comedy Central in 2009, he returned to the writing staff. In the same year he also wrote an episode of the American version of Sit Down, Shut Up.