Strange Mechanical Butterfly

Hello, denziens of the post-apocalyptic badlands of 20six. I'm here to tell you about a strange card I received this morning. Perhaps your latent detective skills will help me to solve this strange mystery.

I woke up very late for work this morning, and only had about fifteen minutes to eat breakfast and shower away the spunk and grime from the previous day's adventures. Ignoring the pressing hands of time, I stayed in bed till the very last minute and watched King of the Hill, in which the eponymous hero was confounded by yoga.

One 90 second shower later, I was running for my train, with card in hand, scooped from the mat in the style of a relay racer (had the previous person in the relay team had a heart attack and dropped the baton to the floor). Amazingly, I made it to the station with a full 20 seconds before my train was due to arrive. I relaxed somewhat, and decided to open said mail, just as the train was pulling in to New Malden station.

As I opened it, a strange mechanical butterfly flew out and hit me in the face, while making a loud "whzzzzzzrrrbbbrrrtt!" noise.

I was so surprised I nearly missed my train, and had to jump in while the doors were closing with that insistent 'beep beep beep' noise. A Korean woman, who presumably had watched all this, chuckled at me. I smiled confusedly back in acknowledgement.

The card features no address or signature, just SURPRISE written across in large letters. The handwriting looks vaguely familiar, yet fills me slightly with impending doom. Oddly enough, though the letter has a stamp, it hasn't been processed so it doesn't have a convenient postmark on the front. So I'm thinking that the stamp was put on just to try and mislead me.

Any thoughts? Or, anyone want to own up?