creep on (someone or something)

slang To observe, investigate, or become overly familiar with someone or their personal matters in an intrusive or undesirable manner. I felt a little weird creeping on all his social media posts like that, but I wanted to know what he was like was before going on a date with him. Some guy in the corner has been creeping on us all night long. Let's go ask the bouncer to deal with him. I didn't mean to creep on her SpaceBook page so much—I just wanted to know more about her because I thought she was really cute.