In the 7th season, in what appeared to be an attempt to appeal to a more
mainstream audience, the producers hired Shane Sweet to play the
recurring character Seven.

The storyline (in the 7th season opener) is that relatives come to visit
the Bundys and stick them with their kid.

It quickly became clear that the fans were not happy with the new
direction or the new character. The writers at first wrote fewer lines
for him, and then wrote him out altogether. His disappearance was never
explained in the show, although "Rock Of Ages" (NOT his last show) hints
at an explanation.

Shane Sweet's last appearance was on "Peggy and the Pirates". However,
his face appeared in two later episodes. I will not spoil the jokes by
explaining this.