Early I mentioned about how oddly certain Special Attacks interact with changed or just non-standard Size
Now I noticed: the same can be said about the most of feats with a Size category prerequisites
What, you will say: loss of prerequisites cause feat to stop working?
Yes...
Unless it's a bonus feat!

It's not a dysfunction, but still, probably, an unintended oversight: Urban Companion
This is identical to the sorcerer's ability to summon a familiar (PH 52), including all benefits granted and gained by the familiar, except as noted below. Her functional level for determining the abilities of the companion is equal to her druid level or one-half her ranger level.
• She does not lose experience points if her urban companion is slain, and she requires only 24 hours to replace one who is lost.
• Her urban companion has total hit points equal to 3/4 her own hit points, rather than half as per a familiar.
•The urban companion gains the ability to speak with other animals of its kind when she has an effective master level of 1st, rather than 7th.
•When she reaches an effective master level of 7th, she can speak with animals of her companion's kind, as per speak with animals. This is a supernatural ability that functions constantly, and it requires only a free action to reactivate if somehow dispelled.
Note: this list doesn't include something like "doesn't qualify for Improved Familiar feat" or "can't benefit from", or something like it

Quote Originally Posted by Flickerdart View Post
Awaken undead
Note: this quote is from the Libris Mortis; updated spell in Spell Compendium lacks that line completely, and older version in Savage Species says:
Awakened undead do not regain any skills, feats, or extraordinary abilities they had in life, but they do gain skill points ([4 + Int mod] × HD)and feats (one for first Hit Die, one for each three HD thereafter) normally after being awakened.