Sydney Sweeney Gets Doggone Dirty in 'Euphoria' Season 3 Premiere

"Euphoria" is back for another season ... and that means Sydney Sweeney is also back as her sexy and kooky character, Cassie.

One of the more interesting -- but not bizarre by "Euphoria" standards -- scenes showed Cassie dressed in a sexy dog outfit, at one point straddling a doghouse and doing other pooch activities.

The point of the moment was to highlight Cassie's new hustle -- selling online content so she can afford her dream wedding. Her fiancé, played by Jacob Elordi, is initially pissed she's thinking of selling her sexiness to make a buck ... but then goes along with it, and has a doggone good time.

There's always a lot of drama on screen for the hit HBO series ... but TMZ debunked some alleged real-life drama between the cast when it was reported SS was kept from a group photo shoot because she and fellow superstar Zendaya allegedly loathe each other.

Of course ... that was not true -- and we got to the bottom of it. Some of the girls were doing a BTS video and snaps while Sydney was off shooting that aforementioned wedding scene.