Producer Jack Burditt tweeted a picture from the set of Tina Fey and Jane Krakowski, who is decked out as her character Jenna Maroney in a bridal veil and shirt with 'sl*t' etched across it.
The Emmy-winning comedy comes to an end this season with 13 new episodes, including an hour-long series finale.
30 Rock creator Fey said in June that she feels the time is right to bring the sitcom to a close after six years on NBC.
"Things do end, and you want them to end when we're running through the finish line and not limping to it, and not vomiting or pooping ourselves," Fey joked earlier in the year.
The show's executive producer Robert Carlock also revealed that he wants Will Arnett and Michael Sheen to make guest appearances in the final episodes.
30 Rock returns on Thursday, October 4 at 8/7c on NBC.
Watch a clip from 30 Rock's season six finale below: