Noel (Patrick Kerr) says that Scott Bakula is appearing at a Star Trek convention in Seattle. However, Scott Bakula's first convention appearance was not until August 2006 in Las Vegas.
The words Frederick (Trevor Einhorn) recites in Hebrew at the beginning of the bar mitzvah scene, are, in fact, the correct last words of the concluding blessing recited following a 'haftarah' - the reading typically done at a bar mitzvah. Frederick then sings the word "ameyn" (the Hebrew word from which the English word "amen" is taken). However, "ameyn" is a congregational response, and should not be said by the person actually saying the blessing. As such, Frederick should not have said it, but everyone else should have but didn't.
Just before the 11-minute mark, Frasier hits the flash button on the camera to escape from Martin, Niles and Daphne. He was standing behind the camera but you can clearly see that his back was hit by the camera's "flash" as well.
When Martin pulls Niles to his shoulder in the church and calls him "...daddy's little peanut man", a young female extra in the background cannot help cracking up.
Frederick (Trevor Einhorn) turns 13 in this episode, but he was already 13 in the Season 8 episode Cranes Unplugged (2001). However, he should be 13, as he was born in November 1989 on Cheers (1982). He was aged too rapidly for a while, but the writers now seem to have corrected this.
When Frasier apologizes to Noel about not getting Scott Bakula's autograph he neglects to return the unsigned photograph to him.