Any scene where Dracula and Chupacabras the castle shop-keeper are on-screen together. With the latter kowtowing to your every whim and praising his excellency.
At some point in the past, Dracula had to have a prison made specifically for Chupacabras to cancel his teleporting, because his pranks and personality were just that irritating.
Drac asks the Chupacabras to read the artifact to open the Mirror on the wall and its challenges. After examining it, being the only one who can understand the language written on it, the Chupacabras conjures the spell...
Dracula: (in an exasperated/skeptical voice) That's it?
Chupacabras: (with a completely straight face) That's what it says, Sir.
The look on Drac's face when Trevor asks him to find all of the broken pieces of the Mirror of Fate after enduring Agreus is absolutely priceless. The sort Dads wear when they can see they are about to be really inconvenienced and would rather not accede to their child's demands but love and honour push them to attempt anyway.
It's a face that screams "I've had a long day, kid."
A Brotherhood knight who meets his demise in Drac's castle is called Eddard S. Notable, in that he's killed not by Agreus or any of the other monsters inhabiting the castle but by his own commanding officer, who cracks under the strain and ends up mortally wounding Eddard because he was the only one brave enough to remain with his crazed superior, rather than flee with the other knights. Poor honorable fool. (He also mentions that one of the trees with red leaves may have had a face carved in it...)
One of the knights in the City of the Damned drank something from the Chupacabra's shop. His last moments of life were spent in a laughing fit at seeing his scroll write out his drunken thoughts (which you read).
When you chew through some ropes as a rat in the theater, a weighted bag comes crashing down. What's written on it? ACME.
Satan's taunts while in possession of Alucard are admittedly hilarious, even if they do reference child abuse.
Satan!Alucard: Aah, don't hit me, Father!
For Christian players, one taunt really stands out: "Join us, Gabriel. Let's form a Trinity!" The Trinity isn't a team, it's the inherent nature of God, and the idea that you can just get three guys - even if they do happen to be a father, a son and an angel - and make one is so outrageously blasphemous even for Satan that it Crosses the Line Twice.
In Revelations, it turns out that Alucard has a bit of humor in him.
At one point, some enemies try to set up an ambush for Alucard. However, it's such an obvious set up that when they finally "spring" the trap, he briefly smirks a bit in amusement.
And then there's his quip to the final boss of the DLC.note Which is also the name of the Achievement you get after the battle
(to Zobek's Lieutenant) Nice armor.
In the Guest House you will stumble across an elevator that would let you continue your quest. There's a blackened plaque nailed to one of the walls of said elevator. What does it say? "No wolves allowed."
You get an achievement for roasting Agreus' owl with a Chaos Bomb, turning it into a fully-cooked chicken (a fully-cooked chicken with salad trimmings on top, mind) like the old games.
The Golgoth Guards are seven-foot part-demon cyborgs who speak in a weird, guttural language and are easily more than a match for a weakened Dracula...but they still have curiously pedestrian worries.
Guard:(after investigating where Dracula was and failing to find him) I need to stop drinking Grog. I'm hallucinating.
The camera shot you're awarded right after you acquire the antidote is humorous as well... when you disregard what's happening in the background. To elaborate, the camera pans out to reveal a fiercely focused face of a Golgoth Guard... while the guy it supposed to be protecting is being dispatched (read: bitten and drained) in a rather gruesome way. Heh.