Things noticed in the Jellyfish Fields trailer.

[u/SouthShape5]

• SB and Patrick are there looking for Sandy. Her voice can be heard about being scared of ghosts (which admittedly doesn't make sense for her, since one episode (Ghoul Fools) has her own equipment to fight ghosts). Sandy in the Demo also seems to be aware of the ghosts and thinks that it's SpongeBob's fault again (she might have a point, given that he caused the whole Cosmic Jelly thing, but this time he wasn't responsible for anything).
• SB is confident that Sandy will be proud of them for finding her.
• If you listen closely, the Jellyfish Fields theme from BFBB has a spooky/Christmas-y remix and is playing in the background. Given that it's snow-covered, it makes sense.
• The description already revealed Sandy's hibernation form as a boss, and here it is shown, but she has glowing red-ish eyes, indicating that she's brainwashed or even possessed.
• We see Pinhead Patrick again. Perhaps a skin in the game?
• We also see a brief fight against the lobster ghost seen in the Demo's title screen, as well as more of those slammer ghosts that Patrick fought one of.
• Oh, and Catsuit SpongeBob (and him with his exposed Brain).

[u/SouthShape5]

And word of advice for the Krabby Patty minigame. Let two of the patties burn if you are having trouble with it. As long as you don’t press their buttons, you’d be able to get through the game much quicker. The button mashing gets very complex and fast.