These pens are realtively new.  They are sharpies 
that are specially formulated for autographs.  I 
have never seen them used on a cel but I have 
seen them used on glossy photos.  Regular 
sharpies do smear some times but these autograph 
pens dry real fast and I have never seen one 
smear.  You may want to give it a try here is a 
link to where you can buy it.  Colors are only in 
black right now: