Mr. Humberfloob telling Joan that she'd better make sure the house isn't as messy as last time, or "YOU'RE FIRRRRRRRRREEEEEE-DUH!" When the camera cuts to her reaction, Kelly Preston is clearly this close to completely losing it.
The Cat's ingenious response to being told that Mrs. Kwan is a babysitter.
The entirety of the "Astounding Products" fake infomercial, where the Cat accidentally chops off part of his tail, making him yell "SON OF A BI-" *BEEP!*
It's more how the timing of this one works. The Cat in the audience covers Sally and Conrad's ears by pressing their heads together and the shot switches to the assistant (also played by The Cat) making that "cut the feed" motion just as he's cussing a blue streak.
And after the scene is over, Cat is seen with his tail bandaged and surrounded by lawyers. He claims "Look, I'm not saying we're going to sue. I'm just saying we have a case" before realizing the camera is on him and moves on.
You're not just wrong, you're stupid! Admit it, that bit was kinda funny.
And you're ugly, just like your mum.
"I'll get you, and it'll look like a bloody accident!"
Cat, after ruining Mom's dress: "Honey, it was ruined when she bought it." (Complete with drag queen voice and sassy finger snaps.)
This exchange.
Fish: This cat is in total violation of... [counts on his fin] ...seventeen of your mother's rules! [phone rings; Cat answers it] Cat: City morgue! Fish: EIGHTEEN!
While ruining the house, the Things use Mrs. Kwan as a surfboard down the stairs. There's just something gold at the fact that she somehow sleeps though the whole thing while the back of her head slams against every step.
The Cat exclaiming "Dirty Hoe" to said gardening tool, then picking it back up and saying "I'm sorry baby, I love you."
The SLOW was initially called the Super Hydraulic Instantaneous Transporter, or SHIT.
The "Third Option: Murder" bit. It's obvious Mike wasn't being serious with that and reminds you a lot of his Dr. Evil persona from Austin Powers.
Cat nearly attacking the Birthday Boy after the groin attack while disguised as a pinata. The kids have to drag him off before he can go through with it.
Before that when he gets hit in the groin by the baseball bat when disguised as a pinata, it cuts to an Imagine Spot with him dressed in a frilly dress and pushing himself on a spring while "Easy Like A Sunday Morning" by Lionel Richie plays in the background with a unicorn there too. According to the commentary, that was the Cat's "happy place".
"Just sign my petition... with this large, oversized pen that requires two hands."
The driving scene. "Wait a minute, two people can't drive at the same time!" "You're right... we should all drive!"
"I think there's something wrong with your brakes, when's the last time you had them checked?" (said while holding the severed brake pedal)
"I dunno, there's this little voice inside my head that's saying, "This is a bad idea", but I can hardly hear that little voice because at the same time an even louder voice is screaming, "LET THE TWELVE-YEAR-OLD DRIVE!!""
"Airbag... standard."
The Cat complained that his eyes were closed when he and the kids' picture was taken. Because he was vomiting.
This line when Cat is introducing Thing 1 and Thing 2 to Sally and Conrad:
"Thing 2 would like to clarify that just because he wears the number '2' does not imply in any way that he is inferior to Thing 1. He says you may feel free to call him 'Thing A', if you like. He will also accept 'Super Thing', 'Thing King', 'Kid Dynamite', 'CHOCOLATE THUN-DA'...Or 'Ben.'"
The bit after where the Cat explains the crate to Conrad, who then points out that it was made in the Philippines. The Cat's response? "Yes, but not this Philippines."
When the Cat says he'll try and clean up the mess he's caused, Sally grabs his bowtie and pulls him down to her level.
Sally: You don't try. You do.
Cat:(nervous) Yes, ma'am. Right away, ma'am.
Upon coming home to see The Mother of All Messes, the Cat gives an I Warned You to Conrad, but points out that on the plus side...
Cat: I think people will be talking about tonight's party for the rest of their lives.
One of the Deleted Scenes, in which Fish calls Joan on her cellphone while the Things wreck havoc in the house; Joan is preoccupied playing Conrad's Gameboy:
Fish: Thank goodness! Mrs. Walden, I have to talk to you...
Joan: Who is this?
Fish: Well, let's say it's... someone you know... someone who sits in dirty water watching you all day...
Joan: Listen, you perv, I've got two kids and a mortgage, so stop harassing me.
Fish:I'm not harassing you, you stupid air breather! What I'm trying to tell you is important!
Joan sets her phone down and resumes playing the video game; back at Fish's end, one of the Things pops out of the receiver, scaring Fish.
In another deleted scene, the Things slow down Joan by pretending the streets are a flood zone. What makes it funny is that there are three versions of this scene before it was ultimately cut. One version had Thing One relieve himself after drinking a truckload of water, the second had Thing One use a giant hose and the third had Thing One blowing up a dam.
of "Cat, Hat."