With post-modernism and hipster irony still seemingly on the rise everywhere, it seems there's just more and more parody bands of various sorts around, often parodies. The large majority of them are pretty crap, because they fail to actually get the point of being a comedy band. For a comedy band to be good, it must observe several rules:
1) It MUST ACTUALLY PLAY GOOD MUSIC. Tom Lehrer got away with his delighful ditties on Gonorrhea and Nuclear Apocalypse because he could seriously tinkle the ivories. Crotchduster flow better than Mr. Bungle and have tight, technically minded guitarwork. Even Tenacious D knew how to rock the hell out. Making the basis for your joke band 'HEY GUYS LETS PLAY REALLY SHIT LOL' is fucking retarded. Mainly because Anal Cunt have already done it. About 30 times.
2) You must have a thorough knowledge and, dare I say it, respect for the thing you're making fun of. Hipsters playing joke metal (see Goblin Cock) will never, ever be as good as metalheads playing joke metal (see Viking Skull, 3 Inches of Blood, etc.). Thus why no metalheads actually listen to Goblin Cock. This is also probably why there is almost no real parody emo around (The one notable exception being Vegan Brownies by the Horn-Rim Jobs). I could never start a parody emo band, because I fucking hate emo, and most emos couldn't do it because they're too bloody uptight. It's almost the opposite to goth, which actually started as a piss-take and then got taken over by terribly serious people with amusing hair (This is why you don't even need goth parody bands: the entire genres been parodying Bela Lugosis Dead for over 20 years now).
3) It has to be all out. Music is, generally, a medium that lends itself better to the expression of strong ideas and emotions. Thats why you get so much music about love, despair, hate, passion etc., and not so much about slight discomfort, or mild anxiety, or something. Fuck subtlety.
4) Swear a lot.
5) Be original. Maybe check to see if your idea has been done before, because if it's good, it probably has. Best example of this I can think of was when one of my mates suggested 'Lawnmower Metal' as a ridiculous metal genre, upon which me and another mate just looked at each other and then played him some Lawnmower Deth. Also, never, never, never rip off Anal Cunt or Tenacious D. Just no.