Killing Kellogg after becoming the Institute leader
SKK Fast Start Institute lets you start Institute quests early.
As a side effect(?) you can begin Kellogg quest after becoming the leader of the Institute. However, all the Synths and turrets won't attack the player because you're the leader of the faction. It almost looks like Kellogg has been kept in prison and the sole survivor finally visited fort Hagen to execute him.
Another funny scene was watching Prydwen entering Commonwealth even though I destroyed it before.