Purple people eater?

[LBReefer]

I realize that's probably the name of an extremely expensive Zoa, but I saw this guy crawling across my office tank this afternoon. He knocked one of my frags over at some point and seemed to just being hanging out. Is he a friend or foe?

And these guys started appearing on the back wall near the overflow a few weeks ago. Should I be concerned?

 

[cloak]

The first picture looks like some sort of Sea Cucumber. I'm not really sure about the second picture, but you might want to compare what you have to some Keyhole Limpets online.

https://www.advancedaquarist.com/2003/1/inverts

 

[KJ]

Sea cucumber and limpets.