Continuity mistake: Ted says that Marshall and he only ate jerky and drank Tantrum on their road trips. In 2-17 "Arrivederci, Fiero" however it's established that Marshall had a rule forbidding any kind of food or drink, even groceries, in his Fiero. (00:01:15)Tanngrisnir
Character mistake: Marshall's whole career focus is saving the environment, so it's a poorly written character choice that he buys plastic glasses to avoid a dish-washing feud, boasting that they can just throw them away. (00:20:10)
Continuity mistake: When Lily goes to the bar with her friend Michelle, Barney says "I want her around all the time." It then cuts from Barney to Lily's slightly shocked looking face, obviously from a previous cut/scene change, sitting at the table with them - she should still be walking to the bar with Michelle.
Continuity mistake: We find out in this episode that Ted and the mother don't get married for several years, due to postponing The Wedding when she became pregnant. They eventually get married in 2020, when their children are 3 and 5. But in Lobster Crawl (8-9), at the end of the episode Lily and Marshal show up to babysit Ted's daughter when she's younger than that, and Ted is wearing a wedding ring. (00:29:00)