That would be the solo part with the birthday boy/girl’s response:
Obrigado meus amigos,
Do fundo do coração
Por me terem cantado
Esta linda canção.
(Thank you my friends,
From the bottom of my heart
For having sang
this beautiful song)
Actually that’s pretty neat, hm? 
I didn’t know the words either (Arnold Winkelried posted them), so it’s not commonly sung here. But I guess there must be places where this song is more popular.
In addition to the ones Bagistan listed, the following Swedish birthday song has been growing in popularity the last few years:
Vad är det för en dag?
Är det en vanlig dag?
Nej det är ingen vanlig dag för det är <name>s födelsedag!
Hurra hurra hurra!
Translation:
What kind of day is it?
Is it a normal day?
No, it’s not a normal day, for it is <name>'s birthday!
Hooray hooray hooray!
Birthday songs in English, French, German, Korean, Spanish, Hebrew, Arabic, Portuguese, and Italian.
Latter-day Saints English birthday songs (from the Children’s Songbook) are:
[ul][li]Feliz Cumpleaños in Spanish[/li][li]Happy, Happy Birthday in English[/li][li]Have a Very Happy Birthday! in English[/li][li]Here We Are Together in English[/li][li]I Like My Birthdays in English[/li][li]You’ve Had a Birthday in English[/li][li]Your Happy Birthday in English[/ul][/li]
Here is a thread regarding the passing of the composer of Happy, Happy Birthday.
So, I was supposed to translate it. :smack:
I celebrate your birthday
As soon as the sun peeked out
And in this glorious day
I ask the Lord for your happiness
Because I think it is
The best gift
Take this hug, I am your friend
Lots of happiness
Take this hug I offer you
And lots of happiness
Yeah, it doesn’t make much sense translated like that.
Another traditional German one is “Hoch soll er/sie leben”, which is a bit like “For he’s a jolly good fellow” in spirit:
(er = he, sie = she)
Hoch soll sie leben
Hoch soll sie leben
Drei mal hoch!
Sie lebe hoch (sie lebe hoch)
Sie lebe hoch (sie lebe hoch)
Sie lebe drei mal hoch!
Long may she live
Long may she live
Three times long!
May she live long (may she live long)
May she live long (may she live long)
May she live three times long!
(the third line isn’t a perfect translation; it’s more like “Three cheers for a long life” than it is “live three times as long”)
Medieval:
May the candles on your cake
Burn like cities in your wake
That second one sounds like “Oh My Darling Clementine”.
Usually while drunkenly watching the screen at a karaoke bar.
Happy Baasday Tsu You
Happy Baasday Tsu You
Happy Baas…day… uh? Whuzzat say?
…Happy Baasday Tsu You
My brother, who is a naturalized Canadian, sings:
Which I personally love.
But I think that’s a free-spirited-I-know-a-bunch-of-obscure-songs-because-I-am-a-musician thing, and not a Canadian thing.
:eek: 
Git outta here. No, seriously, cite? Who had medieval birthday cakes? With candles yet?
I stand ready to be enlightened and gobsmacked.
This is actually an excerpt from the Viking Birthday Dirge… popular at Ren Faire’s and SCA events all over the U.S.
THE BIRTHDAY DIRGE
It's your Birthday! (thud!) Happy Birthday! (thud!)
Doom and gloom and dark despair
People dying everywhere!
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
May the candles on your cake
Burn like cities in your wake.
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Your servants steal, your wife's untrue
Your children plot to murder you
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Burn the castle and storm the keep
Kill the women, but save the sheep
For your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Birthdays come but once a year
Marking time as Death draws near
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Now you've aged another year
Now you know that Death is near
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Now that you're the age you are
Your demise cannot be far
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Black Death has just struck your town
You yourself feel quite run-down
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Burn, then rape by firelight
Add _romance_ to life tonight
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Indigestion's what you get
From the enemies you 'et
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
We love children, yes we do
Baked or broiled or in a stew
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
May your deeds with sword and axe
Equal those with sheep and yaks
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
This one lesson you must learn
First you pillage, then you burn
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
While you eat your birthday stew
We will loot the town for you,
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
We brought linen, white as cloud
The women sit and sew your shroud
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
Just be glad the friends you've got
Haven't found out you-know-what
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
I'm a leper, can't you see
Have a birthday kiss from me
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
It's your birthday never fear
You'll be dead this time next year
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
So far Death you have bypassed
Don't look back, he's gaining fast
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
You must marry very soon
Baby's due by next full moon
On your Birthday! (thud!) Happy Birthday! (thud!)
It's your Birthday! (thud!) Happy Birthday! (thud!)
When you've reached this age you know
That the mind is first to go
On your Birthday! (thud!) Happy Birthday! (thud!)
Link to the website:
Klytus, that Birthday Dirge is wonderful – sounds like Terry Pratchett.
In Chinese, they have the same song. It goes:
Zhu ni sheng ri kuai le
Zhu ni sheng ri kuai le
Zhu ni sheng ri sheng ri kuai le
Zhu ni sheng ri kuai le
You have no idea how irritating that song can be until you eat at a Chinese McDonald’s and hear it played on a cycle repeatedly. For some reason, the Chinese record children’s singing with this super annoying, unnatural sound.
It makes me cringe just to think of it.
By the way, it translates pretty much to the same meaning. I hate this song!
Nothing to add, it’s just that it’s my birthday :).
I’m sorry, now I have no idea what to sing! 
Happy birthday, anyway!