I don't think it's really nice to do that because in my opinion (and this happened to me) it's not really nice and may hurt the other person. Maybe don't directly say it and rather ask them do they know the character from the game their character looks like. But don't put yourself down because of that :)

Not you marky lime compared my oc to undertale-

???? Dude I’m not even talking about u it was someone else

Its fine i deserved it..

Omg I do that too I was about to cause I literally happened when I did a post :0