Ichabod, being played as The Skeptic since the beginning of the film, visibly and audibly shaking (with his teacup and saucer) after being told the story of the Horseman.
When the heroes are running to hide in the mill, Lady Van Tassel clearly says "Watch your head!" which is funny because they're about to lose it.
Upon seeing a spider crawling across the floor, Ichabod gasps and yelps, jumps up onto a chair and refuses to come down until Masbath deals with the arachnid.
"Kill it! No, no! Stun it!"
Ichabod clearly BS-ing his way through an investigation of one of the Horseman's victims shortly after he arrives in town (followed up by being able to expertly determine some previously-unnoticed details of the beheading using some chemicals and tools from his nifty black bag).
Ichabod after realizing that the Headless Horseman is real, complete with this dialogue:
Ichabod:(sitting up in bed completely scared out of his wits) It was a headless horseman!
Baltus: You mustn't excite yourself.
Ichabod: But it was a headless horseman!
Baltus: Of course it was. That's why you're here.
Ichabod: No, you must believe me! It was a horseman, a dead one. Headless!
Baltus: I know, I know.
Ichabod: You don't know because you were not there! It's all true!
Not to mention Crane's bumbling investigations ("You must never move the body!" "Why?" "Because!....")
The fight between Ichabod and Lady Van Tessel. Even though he's The Hero and does his best to try to stop her, it's pretty funny to see Ichabod who has no trouble defending himself somewhat from a dead horseman getting beat up by a woman twice his age.
It's also kind of funny that he defects to a nation that abolished slavery in 1865, while England did it first in 1833. (Though of course, he's in no position to know that.)
When the Horseman kills the priest, it also takes off the top of a "Caution: Horse Riders" sign, leaving it headless.
Probably unintentional but, when Ichabod and the Horseman fight at the cemetery, pay attention to the Horseman's body language: Ichabod repeatedly whacks the Horseman with his shovel, the Horseman does his Implacable ManNo Sell routine, then pushes Ichabod and slowly walks away. Then Ichabod gets up and whacks him again, causing the Horseman to lose his patience and just slap the living crap out of Ichabod. It's pretty clear the Horseman is getting sick of Ichabod's shit.
Ichabod's reaction to being told that the polygraph machine knows whether or not he's telling the truth:
Ichabod: The machine knows?
Same scene: Ichabod is describing how General Washington recruited him to fight a secret war:
Police interrogator: General...George Washington?
Ichabod: (with wide-eyed astonishment) Do you know him?
Upon hearing the news that Abbie's planning on leaving in a week, Ichabod immediately insists that she can't, that their fates are entwined now and she can't run away from that, and it's made absolutely hilarious by the fact that he sounds like a petulant five year old.
Due to Ichabod being about 250 years behind in technology, someone (probably Abbie) stuck post-it notes all over his hotel room to identify and explain various items of the 21st century. This includes the electric lights, the shower, a hairdryer, a coffee pot and the television ("it's like theatre").
When Ichabod turns the TV on, it of course follows time travel conventions by playing something horribly confusing—in this case, a clip from Rise of the Planet of the Apes of a chimp riding a horse. What must be going on in Ichabod's mind...
His facial expressions while using them are hilarious, as is the fact that he falls out of the shower in surprise when the water comes on.
Ichabod noting that facial expressions haven't changed much in 250 years and asking if Abbie had been "formerly betrothed" to a certain officer.
Followed by Abbie informing him firmly that, although the officer was her ex, they were "not betrothed. There was no betrothing."
Abbie saying "I will literally pay you to stop talking" and Ichabod replying that he'd happily take her up on the offer, since he has no money, but since she was so nosy about his love life earlier, he felt entitled to be nosy in return.
Andy's griping as he's digging up the bones for the witch.
Ichabod trying to restart the Revolutionary War. Over the tax on doughnut holes.
Ichabod: What's insane is a ten-percent levy on baked goods. You do realize the Revolutionary War began on less than two percent. How is the public not flocking to the streets in outrage? We must do something.
And the earlier "Have a doughnut hole!" conversation.
Ichabod: (affronted) I do not want a doughnut hole!
Then he tries one and, sure enough, he loves it.
Abbie hands Ichabod a gun but fails to inform him that modern firearms can fire multiple times before needing to be reloaded. He fires one shot and drops the gun to the ground.
Abbie introduces Ichabod to her favorite energy drink, which he promptly aspirates.
Ichabod: (sputtering and coughing) ...Potent.
The start of "The Lesser Key of Solomon." Where Ichabod gives a stirring speech on love...to a woman named Yolanda over OnStar. The audience finds out who he is talking to when he responds to her tearful thanks for his advice by thanking her for remotely unlocking the car. (And for showing him how the entertainment system worked.) Yes, Ichabod apparently got himself locked inside Abbie's car.
Ichabod's reaction to Abbie and Jenny pointing guns at each other?
His frustration with the two of them in general, really.
Ichabod pointing out that the Boston Tea Party was known by a less "festive" name in his day.
Ichabod organizing the whole Boston Tea Party as a distraction is quite funny in itself. It does cast new light on his rant about the "insane" 10% tax on doughnut holes and expected public outrage.
Abbie giving Jenny the short version of Ichabod's backstory.
Ichabod has trouble with the plastic packaging of his disposable razor. He tries to bite it open, but quickly gives up.
Ichabod: What is this impenetrable barrier around this instrument?
At Abbie's encouragement, Ichabod getting into the spirit of a baseball game.
Open your eyes, sir! Yes, you! BASKET-FACE! I thought only horses slept standing up!
Abbie applauds his effort...but advises him to wait until the umpire makes a call next time.
Ichabod's annoyance at the various liberties time has taken with Revolutionary-era stories. Especially the one about Sally Hemmings and Thomas Jefferson, which causes him to rant for apparently hours about the slanderous lies spread by the press.
And then getting schooled that, yes, there is DNA evidence to support this and, just to rub salt in the wound, Jefferson plagiarized one of his quotes.
And Paul Revere's Midnight Ride.
"Pardon the interruption, but Paul Revere never arrived in Concord; that was Samuel Prescott's route. And the warning all the riders gave—as discreetly as possible—was 'The regulars are coming.' Not 'The British are coming.' See, we too were British at the time, so that would have been most unhelpful."
Followed by Abby claiming that "her brother Steve" forgot to take his medication and Ichabod insisting that he's the only one that doesn't need any.
There really is no end to the hilarity that is Ichabod caring about historical accuracy in-universe when he's in THIS SHOW.
Continuing the gag of Ichabod not understanding modern-day payment procedures, Ichabod asks where the courts fall on the issue of paying for bottled water.
This become a Running Gag every time Ichabod sees any sort of bottled water. Later, he's obnoxiously slurping his cup of free water. Abbie tells him to enjoy the arsenic that comes with it. Even funnier? The way his eyes cut back to the cup, considering that he can't tell if Abbie's kidding or not.
Abbie tells Ichabod that there's good news and bad news about the manuscript they need to read. Bad news, it's in London. Good news, it's been uploaded online.
Ichabod: Well, that is excellent news. Abbie: You have no idea what I'm talking about, do you? Ichabod: No, I do not.
Then, while attempting to access said manuscript, Ichabod has a little trouble figuring out the computer. He gets besieged by pop-ups and prints the document five times for fear that it will disappear from the screen "like it did a moment ago."
Abbie expresses confusion about the cipher Ichabod has mentioned to her. Ichabod has this to say:
Ichabod: You're flummoxed by a concept that is completely alien to all that which you have known? I can't imagine what that's like.
Poor Ichabod continues to have trouble with the computer, accidentally bringing up an internet porn site:
Ichabod: Well, this is highly inappropriate.
He also thinks that the porn actress is trying to talk to him and so, he responds.
He closes the computer in frustration when he's unable to figure how to get rid of the pop-up. Moments later, he re-opens the computer, apparently hoping that the pop-up has gone away. It hasn't.
When Irving is trying to flee from the Horseman with the head, the Horseman throws his axe at Irving, missing. It hits the wall, where it decapitates a stuffed crow, much like it did back in the pilot for that sign, and perhaps on its way to becoming a little Running Gag in the show whenever the Horseman throws his axe.
Ichabod leaving Abbie a voicemail or, as he calls it, an "aural missive" on her phone sounds like he is writing her a letter. He signs off with "I am, most respectfully, Ichabod Crane."
During said voicemail, he mentions that he's still having trouble fathoming the idea that his voice is actually recorded on her phone. In other words, he's leaving a voicemail without even being sure that it's working.
Again in "Sanctuary," after hearing noises downstairs, Abbie and Crane having a quick, overly-polite debate over who gets to go down the creepy steps first. Crane loses, even though Abbie's the one with the gun. Shereallydoesn't like haunted houses.
Abbie gives Ichabod his Christmas gift (a Christmas stocking) early:
Crane: Oh...you've embroidered my name on over-sized hosiery. How...odd.
Crane VS Skinny Jeans. He is not a fan.
Crane: Surely the first sign of the Apocalypse is skinny jeans.
This is also somewhat meta because Tom (Ichabod) calls them "the devil's trousers."
Meta example: Da Chief Frank Irving, played by Orlando aka Trollando Jones, has to have social media explained to him by his teenage daughter.
In "The Indispensable Man" and its opening, Crane's attempts at using a modern phone are shown from Abbie's perspective, culminating in his attempts with autocorrect. Even she is laughing by the end.
She leaves him a message with a smiley. His reaction is pure gold:
Ichabod: Oh...it's a man's face. I suppose that's...charming.
In "Bad Blood," moments before some very serious Mood Whiplash, this bit after Crane finally gets Katrina out of Purgatory:
My wife is a witch. That's...cool.
Abbie: You need to have faith Jennie: I have more than faith, I'm a mental patient with a gun.
Ichabod wonders how Abbie has 500 friends on her "so-called social network", as he himself only had seven close companions. The following exchange ensues:
Abbie: We use the term 'friend' a lot more loosely these days. Ichabod:Aristotle would be most unimpressed. note This is a reference to Artistotle's Ethics, in which he says that a "friend" is someone who looks out for your best interests, even though no one else will ever know about it.