Just another demo [elapsed time: 20 minutes]_

As you can see, these are still easily removed [by
me], as the original solid watermark was sitting 
on an area of solid color. For best results, an 
opaque watermark must sit on an area of detail, 
and the font should be sort of thick... That way,
with no detail guides, removal would hack the 
image, which is usually easily proved visually..
This can obviously be a problem, since not all 
anime cels are particularly detailed! Clothing
and hands help... Or even just on an edge, since 
cropping is easily proved. ..