The story is odd to me cuz I don't exactly get the joke, LOL. But aside from that, this is VERY well done! The characters were drawn and colored in VERY neat! I also like the second panel is funny because of their expression as well. Surprise is supposed to be Pinkie Pie's "Beta" self before she was changed to what we know as today. NEVER have a cute pony as a plumber. Who knows? Maybe they will put Surprise in an MLP:FiM episode someday. ... And now I can't think of anything else to say, but... keep making funny comics!
The joke is that her "pipes" need "plumbing." I'll let that swirl around in your head for a while...
I agree with this critique for the most part. One addendum I would make is that I don't think that Luna would be quite so informal. Even around her own sister, her diction is very advanced. The term "hey" really stuck out as a head-canon Luna-ism.