How I Met Your Mother often has a degree of surrealism nestled among more serious issues, "Field Trip" was really, really weird. Barney spends the episode deciding whether to get rid of Nora because she might be older than she claimed--simply because she didn't follow Barney's rule of Ewoks. Ted takes his architecture class on a field trip and ends up wandering the city aimlessly instead of just looking at a couple of New York's many, many, many buildings. Garrison Cootes turns out to be a horrible environmental lawyer, taking a bad deal, rambles about the end of the world, and then Marshall gets him back on board saving the world. Robin also dates her therapist Kevin for a while, which even the characters in the show considered creepy.
The episode didn't come together around a central theme and the plots didn't converge into anything substantial. There are funny parts to be found, but a lot of it felt useless in comparison to the numerous issues the episode could have tackled.