It's pretty odd that Kaliningrad/Königsberg became part of Russia. I know why it was done (not that I agree with it) -- removing the supposed threat of "Prussian Militarism" and whatever -- but it's still odd that it became part of Russia.
Was there ever a proposal that Kaliningrad become part of Poland? Or, if it had to be part of the USSR, why wasn't it part of Lithuania?
Yes, but accounts vary:
"Originally, Germany was to retain Stettin, and the Poles were to annex East Prussia with Königsberg. Eventually, however, Stalin decided that he wanted Königsberg as a year-round warm water port for the Soviet Navy and argued that the Poles should receive Stettin instead. "
"Some historians speculate that it may have originally been offered to the Lithuanian SSR because the resolution from the conference specifies that Kaliningrad's border would be at the (pre-war) Lithuanian frontier. "