I think I’d translate it as “The little mole who wanted to know who went on his head.” De could be ‘of’ or ‘about’ but French uses it like crazy where in English it can be left implied. Maybe the first qui could be translated as ‘that’, as a matter of taste, since a mole can be a thing as well as a person. Voulait is past tense so, ‘wanted’. Faire fills a big hole where English uses a more specific ‘do’ or ‘make’ type verbs, so you have a lot of choice when you’re translating it. ‘Went’ seems appropriate for the target audience, as in “went to the toilet” rather than anything too explicit.