Yeah, the joke's you showed up
A kind of jokingly sad last line. Throughout the song Gambino is saying life is the biggest troll. The fact that we will eventually die is when life trolls us, and us being born is setting us up for it.
Given that he himself leaked his own album and ended his song abruptly eight lines before, he’s sending a message to his fans who purchased the album, which ties into all the things happening prior to the release of the album (the “depressed” note and the dark tweets).
To help improve the meaning of these lyrics, visit “Life: the biggest troll [andrew auernheimer]” by Childish Gambino Lyrics and leave a comment on the lyrics box