Substantial caution is necessary with homemade electrical projects. Looking at the home made power squid project several things are problematic:
1. Water pipe PVC pipe is not a rated electrical insulator
2. 3-prong adaptors are cheesy and are not meant to be soldered to. Their prongs may well deflect and conatact each other, creating short circuits and sparking
2.5 My local Home Depot has commercial grade plug end that do what you need for around $2, allowing the PVC caps to be omitted or serve only an ornamental role
3. Electrical tape (or whatever that green stuff is) is insufficient to protect a soldered joint
4. The wire fill, and attendant heat buildup, greatly exceeds the fill volume capacity of a single pole handy box.
While I'm a big fan of DIY projects, resourcefulness and innovation, this is not a safe project by any measure. It does look pretty cool, and I may start putting eyes on my projects(!).
There's a good reason to look for UL labels on consumer products. At least you have someone to blame when your house burns down. This is a fun and instructive project, but if you replicate it, please use extrordinary caution in its fabrication and use. I'm not usually such a buzzkill (really), but this is truly worrisome.