In S6E1, the first episode Bojack is in rehab, four flashbacks reveal his “first” drink.

In the final flashback, the last scene of the episode, his parents are passed out drunk on the couch after the party. There are balloons and streamers everywhere. An old record is skipping on the record player.

Little Bojack in his sailor suit walks in and sees his parents. He unscrews the vodka bottle cap and chugs for a few seconds. When he puts the vodka down, the record stops skipping and starts playing the song.

Little Bojack drinks and the world literally gets better. The sound shifts from the unsettling and eerie skip of the record player to the beautiful swell of violins.

Excuse me while I go scream in a corner.