In several languages, there is a positive idiom or expression which is uttered when someone coincidentally walks in while people were talking about him/her. In some cultures, it is considered to be a good omen for the person in question.
In Greek, the expression is “πολλά χρόνια θα ζήσεις”, which means “you’re going to live for many years”.
In Spanish, the expression is “hablando del rey de Roma (por la puerta asoma)”, which means “speaking of the king of Rome (he shows up at the door)”.
In Korean, the relevant expression can be found in this list of Korean idioms.
I do not know of an equivalent expression in English which lacks a negative connotation. The only one I know is “speak of the devil (and he shall appear)”, which obviously has a negative connotation.
My research also led to “were your ears ringing?” or “your ears must have been ringing”, which seems to a be a neutral idiom. Apparently, it is related to a folk tale that ringing ears is a sign that someone is talking about you. Also, some websites mention a variation, “Were your ears burning?”. However, I have never heard this in conversation. If this idiom does indeed exist, it seems to be the answer, but I would like to know if either or both variations is widely-understood in the UK/USA.
My research also led me to find a French equivalent to the ear idiom, “avoir les oreilles qui sifflent”, which seems to be quite established. This makes it more likely that the English one would exist.
So, is there a widely-understood positive or neutral expression for when the subject of a conversation suddenly appears?