The Brute Splicer. Homophobic as he might be, he will make you laugh until you pass out, guaranteed.
Brute Splicer: The wind be whistlin'. Bye bye, lovah.
As with the original, getting two Big Daddies to fight each other is very funny.
One of the fortunes by the Fortune Telling Machine:
Fortune Telling Machine: Look at it this way: at least it'll be quick and painless.
Immediately after finding the Incinerate Plasmid in an amusement park, a prerecorded announcement suggests lighting the fireplace for an animatronic couple. If you do, the fire travels along a trail of oil and engulfs the couple in flames.
In further Mundane Utility hijinks, the next announcement suggests you light someone's cigarette with your newfound power. However, close examination of the next animatronic setup shows that all of the dummies have been charred to a crisp: was the plasmid too powerful, or were the previous takers just really bad shots? Either one's hilarious.
Plus, oh happy coincidence, there just happens to be a live splicer hiding among the dummies...
In the end credits: "53,596 zombies were killed in the making of this game." It is a reference to the then-popular idea of developers trying to one-up each other in how many zombies are killed in a game, from Dead Rising to Left 4 Dead to Prototype.
In the finale. After you rescue Eleanor and get her a Big Sister suit you get a plasmid that lets you summon her to help you in fights. What does the plasmid's description say? "It's Bring Your Daughter to Work Day!"
If you choose to shoot the guy, the splicer prostitute screams "Not again!"
On the second floor of The Pink Pearl, you encounter a splicer and her john arguing. After killing them both, Delta turns to the coin-operated window... and the guy watching on the other side scrambles out the door, terrified.
In the Fontaine Futuristics level, "Alex The Great" has this to say when you hack a vending machine:
"Well done! You won a battle of wits with a HOME APPLIANCE!"
Gilbert Alexander is the height of Crazy Awesome. Honorable mentions go to preventing you from entering a locked office by singing the Fontaine Futuristics jingle so loudly it interferes with the voice lock, and introducing the first Alpha Series with "I think one of your old co-workers wants to welcome you back to the office".
"How dare you try to buy me out with this-this bribe, this pittance, this sublime... God damn you, Delta!"
Any time you shoot someone with a rocket spear.
The sheer number of traps you can set. Trap rivets, trap spears, proximity mines, remote turrets, even a whirlwind trap plasmid... that you can charge with other plasmids! If you've got a full inventory you can literally fill the entire area with traps while guarding a little sister and just stand there and watch the carnage.
The steps to getting the secret achievement "9-Irony". In Ryan Amusements, after the Journey to the Surface ride becomes open to you, you will see an animatronic Andrew Ryan ready to greet you at the entrance. Leaning against the wall behind him is a golf club. You have Telekinesis. What follows is a niceContinuity Nod.
Sometimes carrying the Little Sisters around in BioShock 2 leads to some amusing commentary:
(After upgrading a weapon at Power to the People Machine) Even Daddy's toys have toys!
(After setting down a decoy) No candy for spooky Daddy.
(After electrocuting a splicer): Look Daddy, he's dancing!
During the teleportation bit after you grab the Unstable Teleport Plasmid, one of the things you randomly teleport to is the sight of the Plasmid floating through the air, apparently chasing some poor Splicer who is screaming in terror and running from it as fast as he can.
Poole's comparing Lamb not charging admission to Dionysus Park in Rapture to "some kinda naturist camp where everybody wears pope hats and nothing else!"
The Ryan Amusements audio tour. "BUT THE PARASITES SAY NOOOOO!"
In Minerva's Den, the Spider Splicers wear horn rim glasses.
"What's that, Father? Teach them about fire? Well, if you insist."
In the room where you find the Booze Hound tonic, you also find an audio diary from a guy offering his friend dating advice, which basically involves a teddy bear and a trip on Journey to the Surface. If the bottles of booze you can find in the immediate area is anything to go by, you can take a pretty good guess how it went.
While Eleanor's childhood diaries are certainly Heartwarming, "Barbarism" manages to be adorably hilarious.
Eleanor: Mum says I'm becoming a barbarian. So I said, "Eleanor eat dog now too... Barbarian happy!" And Mum said "They only think they're happy, because they're selfish and ignorant." Hmmph! "Eleanor think ignorant sound like fun!"