Muppet who is 3 1/2 years old (4)
I believe the answer is:
elmo
(Other definitions for elmo that I've seen before include "Saint associated with fire" , "St ----'s Fire: aura from electrical discharge" , "Saint whose "fire" occurs around masts etc" , "Sesame Street character - patron saint of sailors (with his own fire)" , "Fiery saint" .)