Good boys can't spell

If you head down to the post on Sinter Claus you'll see a note at the end suggesting that some of the spellings may be less than accurate. It turns out that about the only accurate thing in the whole post was that note. Correct spellings are as follows...

Zwarte Piet

Sinterklaas

Sinterklaas Kapoentje
Gooi wat in mijn schoentje
Gooi wat in mijn laarsje
Dank u Sinterklaasje

Which at least explains why I was having trouble pronouncing Gooi / Hoy. I am however confused about the spelling of Sinterklaasje only because I'm sure I saw it spelt differently on a poster...