No, it's quite unusual, and no, you would never find it in formal English. It's an imitation of spoken language. The only place you would see this reversed style of speech written down would be in the transcripts of conversations, or maybe a film script. It's sometimes used in stories, particularly to show the speech patterns of characters who are of a lower social class. For example, a farm worker or cleaning lady in a story would speak in this way, to distinguish their conversation from that of more educated people.

Leila Hello. The structure is not common at all, and neither is it "formal". It is just odd. The common structure would be this: I have Looked forward to this day for so long. He is acting in one of your London theaters. Su Ki has given you an excellent answer. .

It sounds like Yoda.