Here is, before all else, one of the FUNNIEST fanart comics I've ever seen in my life. ^_^

Accio Brain

A wonderful example of the delightful rib tickling you'll find when you enter is this, a little Holiday Cheer.

Funny

"Christmas was approaching fast... and great bunches of mistletoe had been hung at intervals along the corridors. Large groups of girls tended to converge underneath the mistletoe bunches every time Harry went past, which caused blockages in the corridors; fortunately, however, Harry's frequent night-time wanderings had given him an unusually good knowledge of the castle's secret passageways. "

Funnier
"Mistletoe," said Luna dreamily, pointing at a large clump of white berries placed almost over Harry's head. He jumped out from under it. "Good thinking," said Luna seriously. "It's often infested with nargles."

Funniest

'Twas the night before Christmas in Gryffindor tower;
each student was snug as a bird in a bower
But down in the dungeons, our Snapey was scheming
and plotting away while the kiddies were dreaming
Snape didn't like Christmas, you see, not at all.
(Perhaps 'cause his cauldron was one size too small)
But this year he would finally have peace and quiet,
escape from the usual Gryffindor riot
Of crackers and dungbombs and god-awful singing.
Snape hated that noise, how it left his ears ringing
He'd hitch up a dog (and he knew just the one)
to a sled, and put in Christmas stuff by the ton
Then he'd take it away and he'd set it on fire,
and do his Snape happy-dance all 'round the pyre
You probably think that his plan can't succeed,
and that someone will stop such a naughty misdeed
But brains and ambition, I'm sorry to say,
trump courage and good intentions any day
So next morning the cry could be heard round the school:
"Merry Christmas to nobody!" Slytherins rule!
-Pirate Monkey "How the Snape Stole Christmas"

Here's a random,. non-HP related funny morsel!
I'm sure many of you have been kept up-to-date on how people have been trying to avoid using the word 'Christmas' because there are so many holidays around that time, and they don't want to offend people.
Well....

"Personally, I'll wish people a Happy Chirstmas whether their Christian of not. I'm not, but I don't get upset whenever someone forgets to say 'Happy Yule'. I mean, just yesterday someone bought something where I work and I accidentally said  'Have a nice Christmas'! They turned and glared at me "I'm Jewish."
"Oh." i said, immediately contrite. "The I hope you have a TERRIBLE Christmas."
Can't these people just take it with good intentions?"
-Nefarious Cretin