"J.J." in the 70's sitcom, Good Times, took over that show, lock, stock, and catchphrase -- "Dynomite"!!! The show was originally suppose to revolve around the parents trying to raise their family in the ghetto.
Seven of Nine didn't "take over" Voyager. Not the way "JJ", The Fonze, Alex P. Keaton, Urkel, took over their shows. Those were initially minor or background characters who became the only thing fans thought about when they heard the names of the shows. With Seven, it was only that way among a fraction of Voy fans. I think this is a "thing" among Voy fans, the debate about Seven and the Doctor "taking over" Voy. She was simply one of the more prominent castmembers.