When Niles says he went only to the 'Or-eh-gone' border because of the fresh fruit not being allowed past it, he was wrong (likely due to the show being taped in CA). In reality it is the California border which holds back fresh fruit when one enters from OR or elsewhere. This is due to the enormous farming industry in CA and the danger of introducing foraging insects into it, which could wreak much havoc to the plants, let alone the financial repercussions for damaged plants/crops. Oregon and Washington don't have the fresh fruit restrictions, normally.
When Frasier addresses the sensory deprivation booth and speaks of Maris' affair, he mistakenly thinks that Maris is inside. When he opens the booth, he discovers Niles instead, looking sad and forlorn from learning of his wife's transgression. But being inside a sensory deprivation booth, Niles would not have been able to have heard anything Frasier was saying.
During his tussle with Gunnar, Niles leaps onto the hearth of his light fireplace and places his hand on the underside (i.e. fire-facing) surface of the fireplace's metal surround, keeping it there for several seconds without the certain severe burns that should have resulted.