When they try to lure the Evil Thing to them with a recording of its mating call. Just as it gets close to them, they press the wrong button and begin blaring hip-hop.
At one point Max has an extended sequence of brushing his teeth... before taking another bite of a cookie before even leaving the bathroom, making the entire scene pointless.
"A Creature Was Stirring": The end where the Krampus turns out to be a Christmas present brought by an SUV-limo riding Santa Claus.
"Poof de Fromage": Just the thought of alien leeches posing as cheese curls is one of those things that's funny because of how Jean-Louis (the alien posing as a French exchange student) takes it seriously.
The Answer Cut when Bobby asks what happened to the real Jean-Louis (since the boy known as "Jean-Louis" staying over his house is an alien posing as a human boy): The real Jean-Louis is tied up, stripped of his clothes, and left in the unclaimed baggage area at the airport.
Part two of that episode gives us this gem right after John, who was turned into a tick creature, was on the receiving end of a Groin Attack. The actual impact occurs off-screen, but the dialog makes it obvious what happened:
Nathan: Ooh! Right in the...
Lisa: In the what? Does he even still have any?
(John doubles over in pain)
Nathan: I'll take that as a yes.
Big Yellow dancing in "Mascot"
"Terrible Love": A rather darkly funny one: Stuart comforts Maggie — who just saw Brendon fall down the stairs after telling Cupid that she wanted him to leave her alone — and signals Cupid to shoot her with his love arrows. Maggie drops dead and wakes up a few minutes later, blissed out and in love with Stuart.
Cupid sarcastically whining, "Oh, no! Not a scene partner." when Maggie calls upon him to give Brendon another love arrow.
Ethan trying (and failing) at learning how to be a cowboy in time for his shootout with "Mad Dog" McCoy in "Coat Rack Cowboy."
"Uncle Howee": Uncle Howee posing as a police officer after Jared threatens to call the cops on him.
The name of Uncle Howee's game for Jared to play: "Find Your Sister Before Mom Gets Home and Grounds You For the Rest of Your Life."
"Near Mint Condition": The cheesy commercial and jingle for the Robo-Bear toy commercial, which adds to the episode being a giant Take That to obsessive toy collectors and 1980s nostalgia (Ironic, given that the channel that airs this series airs My Little Pony: Friendship Is Magic, which is a reboot of an '80s cartoon and has its share of obsessive fans and collectors).
Ted telling his brother that he's not sure how to get rid of a cybernetic teddy bear that was recalled for killing and maiming children, because they're not like werewolves or zombies, which have well-known ways of being destroyed.
Like Uncle Howee before her, Mrs. Worthington (of the episode of the same name) has a few great one-liners when she's not being horrifically sadistic. After Nate reacts with shock when she puts eyeballs in Molly's dinner, she thanks him. Later, she cheerfully calls out "Is your mother a blond or a brunette?" while blithely knitting a voodoo doll to torture the woman.