SteamPoweredKleenex It's not uncommon for stuff like this to actually exist in an official capacity. I remember seeing style guides for Star Wars and Doctor Who comics where they had specific sound effect spellings for the TARDIS dematerializing or a lightsaber being turned on.
If this guy went by the licensed comics, he's just re-creating their in-house styles. I suppose he could be doing worse things out on the streets, so I applaud his restraint in confining himself to YouTube.
fluffy I asked the webcartoonist about the provenance of the particular onomatopoeia and style, and he said that the original comics were done by someone who hadn't seen the original show and only had promotional photos to go off of. So he's basing it on his impression of how the things sounded in the show.