The episode, "Still," will be pushed back to Monday, April 29. The episode that was scheduled for April 29, "The Squab and the Quail," will air in place of "Still" on Monday, April 22.
This isn't the only programming move by a major network in the wake of the Marathon events. NBC pre-empted Revolution Monday in favor of news coverage, and Fox pulled a March Family Guy episode from Fox.com and Hulu after someone created a mashup video that made it appear as if the show was depicting the deadly explosions at the race.
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