OK, I re-watched this last night.
Some funny moments. I know this was a comedy episode, but some were better than others for me.
Completely out of order:
I loved it when Ianto cut in on the dancing and Gwen thought he was asking her to dance, but he was aiming for Jack

Rhys going after the alien with a chainsaw, and the saw dying on him

Rhys and Gwen's parents were a bit too OTT, but I still found myself laughing at the sniping between the two mothers.
Are we going to get a subtle reminder, every episode, that Owen is now dead?

Although the not so subtle banter between Jack and Ianto when Ianto sticks up for Owen, stating he never speaks ill of the dead was good

Speaking of Jack and Ianto - I love the throwaway lines that bring their relationship slamming into you. No hiding from homosexuality in this show

. Jack telling Gwen he'll do the 'usual' - and including Ianto in the list

How do they get around the fact that Gwen and Rhy's families won't remember the wedding? Or do they implant false memories?

Ianto telling Jack so matter-of-factly that the situation is not contained

At first I thought the bridesmaids must be so thick to not realise something was up when Gwen suddenly appeared heavily pregnant, after not being so the night before. But the I thought more realistically - how would you deal with something like that? You would assume you were rat-faced and didn't notice the bump. People just don't get that pregnant that quickly!
I thought Rhys was out of order telling Jack to stay away from the wedding. What has he got against Jack? As far as I remember, he doesn't know that Gwen has feelings for him? And it's Gwen that lied to him, not Jack etc. So why does Jack get the flack? Or is it because Jack is the boss, and so obviously is to blame - because the blame Gwen would be the end of their relationship?
Gwen is still so two-faced. She obviously loves Rhys - loves him a lot. But how can she stand there and say he's the only one for her, when just seconds before she's been making eyes at Jack??? Although I don't envy her situation - loving two men at the same time. (Not that I really but Jack and Gwen. I just don't see it).
And we know Jack was married once. More little snippets into his past life...
I know there's a lot more. But memory fails me...