User blog comment:Greatbuddha/Introducing irregularities in a conlang/@comment-3306652-20120708210445

I agree with Rostov, natural languages imply a natural ancestor - which sound changes have affected, and with a root structure similar to ccvc or ccvcv, quite a few changes could occur. Assuming that you're language is agglutinative, adding affixes could for example make unstressed syllables collapse, thus creating consonant clusters that could get simplified. Other common examples are elision of intervocalic stops, which causes hiatus or in some cases synaereses.

Sometimes it is possible to "simulate" irregularity through transfixes and radicals similar to Semitic languages.

Another very common example would be to let verb paradigms contain the typical front vowels, which then may affect preceding stops, creating palatals, fricatives or affricates.. Random example:

te > ze/tie/ce/cie

Also simulated irregularity.

After all, irregularity lives up to its name, and is... Irregular.