Jeeves is incorrect when he says that there are only two irregular verbs in Japanese. Suru and kuru are the only two that are highly irregular in most forms.

Some verbs are only slightly irregular in a few forms, but are irregular nontheless. A list of other verbs from memory:

Some verbs which combine with "suru" do not follow the conjugations of "suru" in some forms. "Yaku suru", to translate, is "yakuseru" in the potential form, and not yakudekiru. This does not apply for all verbs which use suru.

Most, if not all verbs used specifically as honorifics are irregular. E.g., nasaru becomes nasaimasu, and not nasarimasu.

The verb iku, to go, is irregular in -te (itte), and -ta (itta).

Kureru has an irregular bursque imperative of kure.

Aru is conjugated as "nai" for the negative.