I always liked on 'Married With Children' the executive forced child character that was wedged in was gone the next season and the only acknowledgement he ever existed was his photo on a milk jug.

With the notable exception of Malcolm in the Middle.

Baby Jamie wasn't brought in as any way to boost audiences, but rather because the actress playing the mother was pregnant in real life and the writers decided that instead of hiding it, they'd work it into the series.

Considering the show didn't have any dips in quality throughout the saga, it's a rare situation. It's the one show I can think of where a baby was brought in and the show still felt the same (in a good way) both before and after.