I was relieved as much as pleased to see Illyria change into Fred for the duration of her parents' visit because otherwise we would have been wrapped around the axle with a story of the Burkles and how they reacted to the loss. That may have been at least one or two episodes of emotion-laden non-entertainment with them asking why and what was going on and being filled in on a subset of what we already know. This is also the first clue we get that Fred has not been completely annihilated - Illyria, who has never had to act like anyone else before, got Fred and all her mannerisms completely correct. Just like Spike, Fred was one of those characters who was a fan favourite and the writers still may have been hoping to get picked up on another network where they would be able to figure out how to reconstitute Fred in Season 6. To follow up on what
@Lyri said:
ILLYRIA as FRED
(in a lower voice, as Illyria)
Your grief hangs off of you like rotted flesh. I couldn't tolerate it from them as well. I thought this would be more convenient.
WESLEY
How's it possible?
ILLYRIA as FRED
(in a lower voice, as Illyria)
It's a simple modulation of my form. I appear as I choose.
(cocks her head, looks closely at Wesley)
Do you wish me to stop?
Yes, she did this as a convenience to herself, but when she says "I appear as I choose", she would have come from an era when marriages were arranged and would not have tried to shut her mother up during this exchange:
TRISH BURKLE (to Wesley)
Well, I want to hear absolutely everything, but most importantly, have you got a young lady in your life?
FRED
Mom!
TRISH BURKLE
What? I was just asking. Well, can I help it if there's a perfect gentleman hiding in plain sight of my single daughter?
FRED
Dad, make her stop.
There is no correlation between the customs of any society in Illyria's time and this reaction. This made me hope that there would be a recovery plan for Fred that might materialize with Illyria sharing an existence with Fred the same way Glory shared an existence with Ben. If Fred had been annihilated, Illyria would not have been able to draw on her appearance, mannerisms and understanding of modern family dynamics.