Irregular verbs in German can change in any person, not just in the second and third person. For example, the verb "sein" (to be) is irregular and changes in all persons:1st person singular: ich bin (I am)
2nd person singular: du bist (you are)
3rd person singular: er/sie/es ist (he/she/it is)
1st person plural: wir sind (we are)
2nd person plural: ihr seid (you are)
3rd person plural: sie sind (they are)So the answer is that irregular verbs in German can change in all persons.