I think I might have seen something like this before, but for the love of TPT I can't seem to find it anywhere. Oh well, I wrote a Soapworm creator myself. It's available on the script server.

It shows up as a new element called "SPWR" (Soapworm) in the Liquids section, with the same colour as SOAP. Draw a line of SPWR and you get a Soapworm. Simple as that. I'll try to link a GIF, hold on.

EDIT: Three config options have been added, which can be modified from the console.

• tpt.SPWR.spacing: Creates a soap waypoint from each N-th SPWR particles, kill the rest. The above GIF was created with spacing = 1. Defaults to 6, so it won't create toothpaste-like soapworms (like above) but nice, unfolded soapworms instead.
• tpt.SPWR.bubbles: Connects the head and the tail of the new soapworm if they're close enough (in a 6-pixel radius of each other) if set to a truthy value.
• tpt.SPWR.callback: Called (pcall, it's safe to set it to anything, errors are reported) whenever a SPWR particle is turned into a SOAP particle. The ID of the new particle is passed. Example:

tpt.SPWR.callback = function(i) sim.partProperty(i, "dcolour", 0xFF000000 + math.random(0, 0xFFFFFF)) end

EDIT: Added link to the version on the script server.

EDIT: Example save (dunno why I hadn't linked this before)

I'm glad you all like it. I'd like to make it so the bubbles it creates actually pop when one of their links is broken, but as far as I can tell, that only happens when life is 0 and that somehow prevents the creation of bubbles to begin with.

I like how it's possible to add meta-elements such as SPWR to TPT. Maybe others have got other meta-elements in mind? The trick is to use the graphics_func and kill (or change-type) the particle immediately.

Oh, yep, the one I'd submitted to the script server was a bit dated. Thanks for noticing, jacob1.