I think Surprise! From season 6 is a good example of the more lighthearted, funny side of the show. Lot of great jokes and gags, and we get a sweet moment between Bojack and Diane with the AA Chip.

Not the best for introducing the story since a lot happens leading up to this, and it does spoil a bunch of stuff, like the fact that Bojack becomes sober, PB and Diane divorce, PB gets engaged to Pickles, cheats on her with Diane, and PC eventually adopts a baby

The best episode for introducing the story would probably be the first episode of the series, but it shows some of the best humor in the show while not getting too emotional or heavy like Free churro or That’s Too Much Man

Also wondering if they have any jokes that actually break the 4th wall