At the end of the episode Morty briefly develops super-intelligence because he has *ahem* ingested the seeds, but this effect wears off very quickly and is followed by highly unpleasant side-effects. Morty undergoes horrible suffering over these seeds, but Rick shows a complete lack of sympathy for him. He never specifies: Rick keeps reiterating that they are very important but never explains why.However, Rick convinces them to let him stay by tricking them into believing that he is a good influence on Morty. (Funnily enough, these messages were never passed on.) Even Beth, who loves Rick, agrees to sending him away.
Rick justifies his lie by saying 'It's a figure of speech, Morty. Trivia and Interesting Information From This Quiz
