The opening scene, in which the dog systematically goes through the entire house to munch on whatever snacks the family members had with them when they dozed off. It's like the dog's seen Dad fall asleep in front of the television so many times, it considers that the signal that it's safe to go chow down.
Later on, Robbie can be heard complaining that "someone" got crumbs in his bed.
The parents getting high and giggling in bed only to have to pretend to sober up in a hurry once the terrified youngsters pile in with them is hilarious (and, um, relatable). Diane frantically waving smoke is the cherry on top.
Steven:[repeatedly pooching out and sucking in his gut in front of the mirror] "Before...after...before...after..."
When Diane first realizes how big / scary the problem the family faces is, during the first night Dr. Lesh stays at the Freelings' house, Lesh (an, if Cloudcuckoolanderish, still seemingly pretty prim and proper lady) offers Diane a bottle of booze. Next morning, Lesh asks Diane how she is, and Diane, instead of answering verbally, just turns the bottle upside down to show she has consumed every drop of the booze.
Carol Anne being rather blase about the poltergeist activity in the kitchen. First she yawns when Diane demonstrates a chair sliding across the room, then declares that she wants pepperoni pizza when Diane repeats the trick with her.
When the pool construction guys verbally harass teenage daughter Dana, and Dana blatantly gives them the finger in response. Bonus points for Diane seeing it and also chuckling about it.
The scene in the first movie when Tangina and Diane argue about who should go into the Portal.
Tangina: You never done this before!
Diane: Neither have you!
Tangina:[Beat] You're right, you go!
When Steven tries to answer Tangina psychically, it seems like she didn't hear him, but...
Tangina: I just don't like trick answers.
The final shot of the movie, where the family enters a hotel room and then shoves the TV outside, is pretty comical.
When the family brings Dr. Lesh and her team in, Dr. Lesh's reaction to seeing the poltergeist activity in the room is pretty hilarious. A jump cut shows her sipping coffee/tea, using both hands to hold the cup because she's shaking too much.
One of Dr. Lesh's assistants talks about a previous case where he videotaped a matchbox car traveling across a room by itself, taking 7 hours to get from one side to another. Steve just goes "uh-huh" and opens the door to Carol-Anne's room and walks away, leaving Dr. Lesh and her assistants to stare at all of the stuff flying around the room.
Dr. Lesh saying it'd be hard to determine whether the house is haunted... followed immediately by a coffee pot sliding across the table all by itself.note Of course, she's defining the difference between manifestations. Hauntings are permanent, poltergeists are not.
The "remote duel" in the beginning, where the Freelings' TV remote control interferes with their neighbor's, and both families keep changing each other's channels.
"Awwww... shit, Tweety, couldn't you have waited for a school day?"
The Freelings look for help in the Yellow Pages.
Diane: "'Furniture Movers,' we got."
Poltergeist II: The Other Side
The car being angry as a Running Gag. Apparently according to Taylor the car is sentient and only works when it wants to. As seen in the finale of 2.
Steven: You can stay in the house, you can have my aura, my spirit, the ghosts, the whole deal. The WHOLE CASABA!!!!! But keep your hands off my car. Hands off!!! It's worse than it was before.
Taylor: The car's still angry huh?
Steven: Angry? That car is PISSED!!!
The end of the movie, with the family with a realtor looking over a new home. The house gives off such a creepy vibe that the next thing the realtor hears is the family cranking up their car and fleeing.