This is actually Fune Isono, Sazae's mother, fixing tags. And this is the last thing I ever thought I'd see in my life.

That's a pun for "nyotai-mori on Fune" and "Funa-mori (舟盛り, fune-mori)", sushi/sashimi on a boat-style-box.

EDIT: See also: http://pixta.jp/tags/舟盛り