Tac Tics are mints that come in little plastic containers. Bart swaps Marge's birth control pills with Tac Tics. When Marge discovers what Bart is doing, she throws the Tac Tics out of the window. Nelson comes along, picks up the container and eats them, not knowing that the Tac Tics are actually birth control pills.
Behind the Laughter
Tac Tics are an obvious parody of Tic Tacs.