I have found a 1900 federal census listing in Cicero/Berwyn, IL for a "Charles" Klecka. Seems Kajetan or the census taker changed his name to Charles. His wife is listed as "Mary" even though I know her name was Marie.
My guess is possibly they could either not speak enough english to convey their names. Kajetan is a tough one, or the census taker was a bad speller.
The two sons were Jerry and Joseph. Jerry the oldest (my ggrandfather) was born in Bohemia, 1887. Joseph the youngest born in Illinois, 1885.