What happens when a master shares the Alter Self spell with his familiar?

Question

A wizard's familiar gains the supernatural ability share spells that says

At the master’s option, he may have any spell (but not any spell-like ability) he casts on himself also affect his familiar. The familiar must be within 5 feet at the time of casting to receive the benefit. If the spell or effect has a duration other than instantaneous, it stops affecting the familiar if it moves farther than 5 feet away and will not affect the familiar again even if it returns to the master before the duration expires. Additionally, the master may cast a spell with a target of “You” on his familiar (as a touch range spell) instead of on himself. A master and his familiar can share spells even if the spells normally do not affect creatures of the familiar’s type (magical beast). (Player's Handbook 53)

The wizard casts the 2nd-level Sor/Wiz spell alter self [trans] (PH 197) on himself and shares that spell with his familiar. The wizard assumes the form of a troglodyte (Monster Manual 246–7). However, the spell alter self only allows an affected creature to assume the form of a creature that possesses the same creature type as the affected creature, and the wizard's familiar's type is magical beast yet a troglodyte's type is humanoid. (Likewise, size is an issue with the alter self spell: a Tiny creature is typically incapable of assuming a Medium form.)

Despite having shared the alter self spell, does the wizard's familiar remain unaffected by it because the wizard picked troglodyte instead of, for instance, stirge (MM 236–7)? (And, if so, had the wizard instead picked an appropriate magical beast, the wizard obviously wouldn't've been affected by the alter self spell, but would the familiar be affected?) Alternatively, does the wizard using the spell alter self to assume troglodyte form turn the wizard's familiar into a troglodyte anyway, the specifics of the supernatural ability share spells overriding the general rules of the alter self spell? Or, using a different but still generous reading, can the wizard pick one form for the wizard and another, different form for the familiar, the supernatural ability more creating a fresh, effect-yet-to-be-determined copy of the spell than sharing the actual spell that was cast?

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Note: Other conclusions, are, of course, acceptable; the question includes only those I'd considered. Anyway, I feel like this is something I should already know, but familiars have been so rarely used in my campaigns until now it hadn't been an issue. By the way, I did some research, but I figure this was probably hashed out to death on the lost-and-lamented Wizards of the Coast message boards.

Answer 1

I know, these are no official rules but I think it´s worthwhile to consider what Skip Williams wrote on this subject in his Rules of the Game article. According to him you can (even must) assume a different form than your familiar:

You choose a form for yourself and for your familiar or companion. The forms you choose don't have to be the same. In fact, in most cases, they cannot be the same because alter self allows the subject to assume a form of the same type as itself only…

When you share an alter self spell with a familiar or companion, the familiar or companion assumes a form of the same type as its own. While an animal becomes a magical beast upon becoming a familiar, such a creature must assume the form of an animal when sharing an alter self spell. For example, a cat familiar is a magical beast; when it shares an alter self spell, it assumes the form of an animal, such as a dog, a bird or a bat, not the form of a magical beast.

Answer 2

There is really little documentation in this.

Technically, following straight rules, once you cast it, the same spell will have a new, additional target which is your familiar. The result is that both are transformed into troglodites. Since the transformation does not meet the basic conditions to the familiar (Size and subtype), it actually leads to a spell failure, like casting Resurrection or Animate Dead in any undead (Not a suitable target). In this interpretation, the caster is transformed, whereas the familiar suffers a spell failure and nothing happens.

Another interpretation is duplicating spells. If they are legit duplicated, several spells can have distinct effects when duplicated. Hard to demonstrate with most spells, there are clear examples of it, most notably summoning spells. A duplicated summon monster can summon a distinct set of monsters per duplicate.

If the DM understands the spell as duplicated, the familiar can have a distinct, fitting transformation. If it is considered a same spell with an additional target, as it seems to be written, then it simply fails for the familiar.