There is a case in French where a consonant is added for phonetic harmony, like with the R mentioned above, however it is a grammatical rule.

We add a « t » in front of the third person singular pronoun (il) if the verb preceding it does not finish in a d or t; this happens when the verb is before the pronoun in a question.

Va-t-il aller à l’école le lundi de Pâques?
(Will he go to school on Easter Sunday?)

Courra-t-elle pour attraper l’autobus?
(Will she run to catch the bus?)