If you want to get this effect quickly without spending any money at all, and you have a pro-type camera with a removable lens, you can get it by just holding the lens against the opening, and rocking it side to side a little.
It's a pretty common trick photographers and videographers use to get a sort of dream-sequence effect.
If you want to spend some money and have something a little more stable and usable (and less likely to get dust on your sensor), the Lensbaby Edge 80 and Sweet 80 lenses produce a similar effect and are tons of fun.
I did learn that they must be used judiciously. After shooting most of a personal music video with a Sweet 80 wide open, my wife described it as "like watching an ocular migraine".
But lenses can do things that postprocessing can't do, strictly speaking (though it can often emulate well enough to fool most people).
The input to a lens is a field of photons that are:
1. Striking the sensor at different places. In other words, which pixel they hit.
2. Coming into the sensor at different directions.
3. Coming in at different wavelengths.
The 2D image captured by a sensor completely discards 2 and it drops a significant amount of information from 3 on the floor by bucketing all wavelengths into red, green, and blue amplitudes designed to mostly mimic human visual perception.
It's a pretty common trick photographers and videographers use to get a sort of dream-sequence effect.