Snape the Vampire, Crabbe and Goyle Trolls?

[Florence]

No: HPFGUIDX 20461

This Vampire theory has been fascinating, although like others I find 
myself somewhat sceptical.  However it occured to me that Crabbe and 
Goyle have been likened to Trolls, probably just as much as Snape has 
to a Bat.  They look like trolls, talk like trolls (point and grunt) 
and they're certainly not too bright.  How many times do we hear them 
"chuckle trollishly" or somesuch through the books? Is it just that 
JKR likes to liken her characters to animals/beasts, or do people 
think we've got a pair of part-trolls on our hands too?

Florence