While gathered together on Frasier's balcony, Martin, Frasier, and Niles are talking. Frasier mentions "It's just an hour by plane" (between San Francisco and Seattle). Most commercial flights run in the two hour to two and a half hour range between those two cities.
In "Don't Go Breaking My Heart (3)" in the flash-forward to Niles' and Daphne's second child's birth, Niles is holding a girl. In this episode, Daphne gave birth to a boy.
July 15, 2004, the date the wedding should have been, was not a Saturday.
When Niles drops the ring, Eddie is eating from a plate. On a pulled-back shot, Eddie has licked the plate clean; but on the close-up of Eddie, the plate still has food on it. On the next away shot, Eddie is still licking a clean plate.
Eddie's birthday is May 15 in this episode, but in an earlier episode his birthday is said to be on May 7.
When Niles drops the ring, it can be seen bouncing out of camera range and not into the pate.
This episode is not included in the Final Season DVD boxed set.
(It is the 1993 flashback and Daphne, new to the Crane household is just coming from her room)
Daphne: I just found out what that second toilet in me loo is for (laughs) -- talk about a shock!
As we know from Season 2's "Daphne's Room" (when Eddie is drinking from her toilet), Daphne doesn't have a "second toilet" (bidet) in her bathroom. Even Frasier doesn't have a bidet, as we see in Season 2's "Seat of Power".
Daphne says that at her "Ugly American Party", among other things, they will "...not use the metric system". Today, there remain only three countries in the world that have not adopted the metric system: the USA, Liberia and Myanmar (Burma).
In the 1998 flashback Martin told Roz that Niles was going to tell Daphne about his feelings for her, however Roz didn't find out about Niles' feelings, in the episode "Decoys" which was in 1999, after Daphne had started dating Donny.
The wigs for Daphne and Roz are clearly fake, as they decided to use hairstyles that the characters never wore in the previous shows.
In the last flashback of the day after Niles and Daphne's first night together, it says the year is 2002, but the episode "Daphne Returns" happened in 2001.
In the flashback of 1996, Niles says Maris is upset at Frasier but Niles and Maris separated near the start of season 3, which was 1995.
Niles and Daphne had their honeymoon in 2002, not 2003.
Daphne asked Niles how he knew how to remove the superglue with acetone. She was the one who actually told him in "An Affair to Forget" when his own hand got stuck on that ship that he and Martin were putting together.
While driving Charlotte, Frasier struggles to put on a "hands free" telephone, but in "How To Bury A Millionaire" (Season 6), both he and Martin speak to Niles on Frasier's car phone which is completely hands free, its controls on the console. It's conceivable that he has a different car, but not likely one with less features.
Frasier's "driving" when taking Charlotte to the station makes no sense if you look at the background compared to his wheel motion.
Daphne is impressed with Ronee's ring until she discovers it was the engagement ring Martin bought for Sherry. She should have recognized it, since in Season 5's "Ain't Nobody's Business If I Do" she was the one who found it in Martin's underwear drawer, leading to that episode's entire plot line.