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.
Mistakes Mary's politeness for affection and falls instantly in crush with her, then takes it way too far, and is utterly oblivious to the fact that he's creeping her out.
Is a very poor driver, and flees the scene of an accident in order to do something that probably could have been handled by airport security based solely on the fact that he was so obsessed with a woman he just met.
Demonstrates a total lack of financial responsibility and gets robbed because he thought he could trust somebody he just insulted. Face it: he wasn't even aware that he insulted her...
Decides to go on a cross-country road trip to be reunited with a woman he only drove to the airport.
Sells a dead parakeet to a blind kid for twenty five dollars.
Indulges in a totally unrealistic fantasy in which he is the ultimate hero and Mary can't wait to throw herself at him, thus demonstrating a complete lack of understanding about the way relationships work.
Insists on annoying the hitchhiker they picked up (admittedly he was planning on killing them both, but they didn't know that), without considering that he might not want to hear the Most Annoying Sound in the world.
Utterly ignores Harry's needs until they are pointed out to him, like wearing two pairs of gloves until Harry says his hands are cold.
Kills an owl with a cork and doesn't realize what's so wrong about that.
Puts laxatives in Harry's tea instead of confronting him directly about seeing Mary.
Still expects Mary to fall into his arms despite the fact that he is a stuttering mess and she's only with him because he has the briefcase.
Lloyd could also be considered a Jerkass Woobie - he travels across the country nearly getting killed/raped in the process just to give his dream girl her briefcase, his best friend steals her from him (so he thinks), and finally learns that she's already married. And to top it off he's simply too dumb and/or crazy to realize that she's completely out of his league anyway.
Never Live It Down: Jeff Daniels has had a very respectable career, but the bathroom scene is the one everyone remembers.
Sequelitis: The Farrely brothers had nothing to do with either Dumb and Dumberer, or the animated TV series. Mediocrity ensues.
Spiritual Licensee: Even though there are only two of them, one might say Harry and Lloyd are practically the 90s answer to The Three Stooges which heavily influenced the Farrelly Brothers.
Took the Bad Film Seriously: The only aspect of Dumb and Dumberer to be consistently praised was Eric Christian Olsen's performance as the young Lloyd, with most critics finding him perfectly believable as a younger version of Jim Carrey.