These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Mark and Juno in general. More than one viewer might have thought this movie was about to take a turn into much creepier adulterous May-December Romance territory with the way Mark kept being so friendly to Juno and the way she kept spending time alone with him, but no, that's not what happens.
Unfortunate Implications: The film was criticized for making teenage pregnancy seem light-hearted and virtually consequence-free. Diablo Cody defended the film by saying that it would have been much shorter if Juno had simply received an abortion.