ID Please - cauliflower slug?

[Ducaroo]

Found two of these before, scraped them off and disposed of them. This one was attached to a snail. Upon removal I noticed it squirming a right itself. Good critter or bad critter? Tanks!

Picasa Web Albums - Ed - Slug
Picasa Web Albums - Ed - Slug
Picasa Web Albums - Ed - Slug
Picasa Web Albums - Ed - Slug

 

[Sadielynn]

I have seen these before but I do not recall what they are I believe it is an aeolids nudibranch in rings in my mind these are not safe but I can not say with 100% certianty tho

 

[thincat]

nudibranchs are hard to ID because they are what they eat and take on lthe coloration of the food they consume. Here are some pictures; Nudibranch gallery