There are a few Marc Davis gags in the attraction, like the ridiculous opera valkyrie and the headless knight. The most notable of his concepts are the stretching portraits depicting normal scenes at the beginning, but revealing more creepy and unfortunate situations as the room lengthens.
The passed-out-drunk ghost under the ballroom table, and the one swinging from the chandelier.
From the Hong Kong Disneyland version, Mystic Manor:
One of the visual gags in the "Mediterranean Antiquities" room. It is an animated painting where a Roman family is dining outside, with Mt. Vesuvius in the background. The volcano erupts and lava covers the family...and then they raise their arms and clink their glasses together!
Even funnier is that the woman standing in the picture, who is waist deep in lava, has a confused expression on her face when that happens.
Albert's squeals of terror sound adorable, and despite it looking lethal, all his misadventures in the exhibits are funny, from him ducking back into a cannon every time a Samurai tries to decapitate him, him screaming as the tikis pin him to the wall, and The Monkey King's statue creating a vortex and trying to suck Albert out. And even funnier, during that sequence, A chubby panda gets sucked out of its painting screaming and lands in another one.
There's also Albert yelling in annoyance as his fez gets caught on a sword at the end and the Oh, Crap! expression on the sarcophagus' face as the scarab beetles move closer to him.
The three singing suits of armor (they are in display cases with the helmets above the armor) are a hilarious Shout-Out to the Singing Busts. What's funnier is that their heads are singing, while their armour and weapons are dancing.
Occasionally the song will be sung in Cantonese or Mandarin Chinese. When the knights do sing it, it sounds absolutely hilarious.
When the Hatbox Ghost's head flies into the box, his hat will turn toward the box and the head inside will look up, as if he's saying "Cool trick, huh?"
Jim trying to get his son to just squash one little spider. And Megan stepping in totally deadpan and whacks the bug herself. Hilarity continues to ensue.
Michael: (about the spider) I don't wanna whack it, Dad!
Megan: (whacks spider) There. Ya happy?
Mr. Evers: No, I'm not happy! I'm trying to show Michael how important it is to whack your own spiders!
Megan: (walking away) Whatever.
In a slightly bizarre combination of funny and nightmare inducing,
Madame Leota: Dark spirits from the grave come forth. Lift us from the black. And show us, show us the way back.
Jim Evers: Dark spirits?! Hey, no dark spirits! Don't you make no dark spirits come out!
In the same scene.
Madame Leota: Tell me, whom do you seek?
Jim Evers: I seek the way out of here!
Madame Leota: Then you must look within.
Jim Evers: I don't want to look within, I want to look with out, are you deaf!?
The scene where Jim finds his kids, but they want to stay and help the ghosts while he just wants to leave.
Megan: They're ghosts, Dad.
Jim: They're not ghosts. We're just having hallucinations from that dinner that we ate. It was that chicken, it didn't taste right.
Emma: (insulted, Emma turns into mist and re-appears right in front of Jim) Hey!
Emma: It's not the chicken!
Mr. Evers obviouslycan't see the Hitchhiking Ghosts sitting in the carriage next to him...
The Traveler Hitchhiking Ghost/Phineas: I could swear he was looking right at me.
The Prisoner Hitchhiking Ghost/Gus: He's psychic.
Ezra and Emma fighting over the reins while taking the Evers family to the crypt.
Emma: Move over.
Ezra: What are you doing?
Emma: If you keep driving, you'll kill us all.
Ezra: Well that's where you're wrong, because some of us are already dead. Ha-ha!
Just three words... The Singing Busts!
Busts: Do, do, do, do, do do!
Jim: Hey guys! Keep it down!
Busts: We'll Keep it down, We'll keep it down, Oh, Yes we will we'll keep it down. Oh, we're driving down a highway nowwww... And we're trying, to, keep, it, DOWNNNNN!
The fact that they got the Dapper Dans to do the singing, is just the icing on the cake.