[Leviathan Crusader]

As it sounds; take any song and change the lyrics to make it funny... of funnier as the case may be. Don't post random crud like "Twinkle twinkle little pie, shoop da whoop, eat your eye." That's not funny.
Stop laughing!
I'd go first, but I don't know any songs and am kinda lacking in wit. Help?

[Mykei]

Me and a friend came up with these for Bad Day (for the chorus part):

You had a bad day,
your dog got shot,
your grandma died and you got AIDS
You had a bad day,
your house burned down
and you found your girl's sleeping around,
You had a bad day
everythings f**ked up
but your ok....

Ya had a bad day

[Leviathan Crusader]

Never heard of the song, but I assume it exists. Good work!

This one, I admit, is taken from a Discworld novel. And you'll only understand it if you're familiar with the Australian song 'Waltzing Matilda'. It's abotu Rincewind the wizard while he's stuck out back in the outback.
Oh and it doesn't rhyme or have any rhythm. Don't take any examples from me here...

Once a moderately jolly wizard camped by a dried-up waterhole,
Under the shade of a tree that he was completely unable to identify,
And he swore as he hacked and hacked at a can of beer, saying,
"What kind of idiots put beer in tins?!"

[Нєяоєѕ Lоѕт Ғдп]

For Umbrella, by Rihanna. (chorus)
When the sun sh1te we'll sh1te together
Told you I'll be an ear forever,
Said I'll always do your friend.
Took an oath, I'm a stick it into your end.
Now that you're raining onto Heather,
Know that we'll still have each other,
You can stand under my umbrella.
You can stand under my umbrella, ella, ella, ay, ay, ay,
Under my umbrella, ella, ella, ay, ay, ay,
Under my umbrella, ella, ella, ay, ay, ay,
Under my umbrella, ella, ella, ay, ay, ay,

I ran out of ideas towards the end.