For example, let's take a 10th wizard/5th Eldritch Knight (from the DMG). The Eldritch Knight gets a "+1 level of existing arcane spellcasting class" for caster level and spells and all that jazz on every level except the 1st. So, this character is a CL 14.
Is this character's familiar based upon a 10th level character or a 14th level character?
And psicrystals. On pg. 22 of the Expanded Psionics Handbook, it says "Psicrystal abilities are based on the owner's level in psionic classes." Aren't prestige classes psionic in nature? What about the Shadowmind from Complete Adventurer? Does their psicrystal go up with them as they advance in levels in their prestige class?