Just found a couple of examples of spelling mistakes on football shirts on the Shirtworks blog including one on a bunch of replica Crystal Palace shirts and one on Manchester United player Anderson's shirt.

Chrystal Palace

In 2004 Crystal Palace made a bunch of replica shirts with their club name spelt wrong.

Andesron

In 2012 Anderson came on as a substitute against Everton wearing the shirt pictured above with his name spelled wrong.

See more misspelled shirts at Shirtworks