Cobbled together from real, unrelated "Family Guy" scenes, the video went viral Tuesday, a day after three people were killed and more than 150 injured during twin explosions at the Boston Marathon.
"The edited Family Guy clip currently circulating is abhorrent," MacFarlane, the show's Connecticut-born creator, tweeted. "The event was a crime and a tragedy, and my thoughts are with the victims."
"Access Hollywood" said the video begins with an animated version of NBC Sports' Bob Costas asking "Family Guy" mainstay Peter Griffin how he won the Boston Marathon. The clip then shows Griffin dialing a number after which an explosion is heard, then repeating the action with the same effect.
YouTube flagged the clip with the warning: "The following content has been identified by the YouTube community as being potentially offensive or inappropriate. Viewer discretion is advised."