Maybe Hec has an opinion on this: What makes a song a novelty song?
Currently I'm listening to "Don't Touch My Bikini" by the Halo Benders? Is this a novelty song? I say, "No, it's too awesome to be a novelty song!"
Interesting question, and one I've pondered since I personally love songs that are funny, but bands that betray too much humor or wackiness are frequently undervalued.
The obvious example being TMBG who (despite their many hardcore partisans) can be dismissed as a "joke band." (They're not, of course.)
Novelty Songs go back to Vaudeville and Music Hall (and much further really, but out of that tradition) and represented a particular type of performer. There were Novelty Dance acts too. The comedy is always foregrounded in such songs and there was also an association with the performer playing a kind of comic type.
The classic contemporary example would be Weird Al who plays a specific comic type (nerd) and writes (mostly) parodies of contemporary hits. He's good at it, cleverly rewriting the lyrics and cheerfully spoofing the essence of the song as well. Or he does effective cross-pollinations like his Yoda/Lola song. Or he writes straight up comedy songs ("White and Nerdy").
OK Go don't write comedy songs, but their videos are very much like a Novelty Dance act. Most especially the treadmill video for "Here We Go Again." Which (unfortunately) means that some people are going to not take them seriously as pop musicians.
"Dick in a Box" is another recent classic novelty song, and video. It's not a song parody, but it does parody boy band video conventions.
So anything that's a parody is automatically a novelty song. That's a constant.
Anything that's a joke about something contemporary and passing in the media is a novelty.
The way Adam Sandler updates the Hannukah Song live to include contemporary references is a classic novelty/comic strategy.
"Do You Wanna Date My Avatar" (both song and video) is a Novelty.
So it isn't just being funny or comic in song. It's foregrounding the humor, often parody, often commenting on a specific cultural event or trend or person that's hot in the media.
Another classic novelty signifier would be the naughty, coded lyrics. That goes way back to those old double entendre Music Hall songs, folk songs and rude R&B ("Big Long Sliding Thing" being about a trombone player), and the Dr. Demento staple "Telephone Man" (the last novelty song to sell a million singles) is a good example. Also, Chuck Berry's last #1 song was a novelty - "My Dingaling."
So generally it's not comedy as sophisticated wit, but usually lower forms of humor. Things that would ping a 10 year old. So here you also get gross-out songs ("Fish Heads") and absurd songs/bits ("Bulbous Bouffant") and fake protest songs ("Carrot Juice is Murder" by the Arrogant Worms).
So, Arrogant Worms are a novelty band, but Bare Naked Ladies is not.
Personally I'd rather listen to the Hoosier Hot Shots doing "From the Indies to the Andes In His Undies" than some angsty emo-boy's complaint rock.