A hilarious video about Len watching Porn. Made doubly awesome by the totally serious tone it starts out with.
We also have Rin Chan Nau! done by Owata-P, in the same vein as the song above. Features Miku and Luka and their crushes on Rin, never mind the two of them rapping at Motor Mouth speed.
Luka's Creepy Toast and Sonika's Creepy Song, both parodying how many twisted Vocaloid songs there are. Especially Creepy Song, which specifically makes fun of all the songs where the vocaloids are killed.
The "Temptation of M" drama series (part 1/part 2/part 3). Features exhibitionism, apparent genderswaps, Miku trying (and massively failing) to be sexy, a number of unexpected cameos, and some of the funniest dialogue, sight gags, and characterization in any Talkloid project.
If Lily Was Like This... Another entertaining character piece, spotlighting the (at the time) new character of Lily. As with "Temptation of M" above, one of the funniest things about it is how good the acting is — it's hard to imagine how much fine-tuning it took to get the character's voices to sound natural.
Leon: Tsunderes in anime are okay/But in real life it's just a bitch.
Rin and Gakupo play a practical joke on Miku on her birthday with a present whose lid was sealed so tight it would snap open. Rin's giggle and Gakupo's laughter after Miku got smacked in the face were a riot.
Haku's Drunken Afternoon - a silly skit (with an equally silly soundtrack) about Haku Yowane just being completely wasted from all her drinking on a fine sunny afternoon, during which she starts seeing Rin and Len somehow flying in the sky above, much to her disbelief. Meiko arrives wondering what the fuss is all about, and makes the obvious conclusion that Haku in her drunken stupor was just seeing things.
This MMD video of Big Al, Kiyoteru, Leon, Kaito, Tonio, and Gakupo singing and dancing to the famous internet sensation Yatta! by the Fake Band Green Leaves. Perhaps the only thing that can top this would be an actual vocaloid cover of the song.
The image progression of Onsen Zabuntl Splash in a hot spring. Takoluka goes for a bath in an onsen...and comes out as steamed octopus.
The bridge of the music video of the cover of Asereje (The vocaloids sing in nearly fluent Spanish, too!), where Kaito and Len appear in swimsuits and dancing like the girls, and when four hands try to grope Miku's butt.
Kiyoteru's cover of the first song mentioned, simply named Oppai Song, with a touch of metal.
This dialogue between Kaito, Gakupo, and Kiyoteru in a karaoke bar, where the fun loving Kaito and Gakupo try to get a very straight-laced Kiyoteru to loosen up. At one point Kiyoteru is made to sing the Cutey Honey theme (with the expected reaction of embarrassment from him) by the other two (though Gakupo joins in singing after a moment). Kaito and Gakupo also try to make Kiyoteru sing Koi no Kayoubi (a song which features Kiyoteru crossdressing, hence he quickly refuses). Kaito then tries to sing Boo*s are Man's Romance with the hopes of getting Kiyoteru to shout Oppai!, an effort also shot down by Kiyoteru. Finally Kaito sings Ne~e? and gets the other two laughing at him.
A bad day in salaryman!Gakupo's life. I didn't know whether to laugh or cry... but I settled for laughing. I Forgot.
This "Talkaloid" (original upload taken down by owner due to personal reasons) where Aoki Lapis is introduced into the producer's Vocaloid family, handled, rather reluctantly, by Oliver and Big Al. Includes some embarrassing moments especially with Big Al. And get a load of Aoki Lapis' giggle when Big Al is reminded of his stint at singing Japanese and is embarrassed by it.
Then there's the Sequel about Big Al, Oliver, Avanna, Gakupo, and Lapis singing Vocal RPG Songs. And Oliver makes fun of Gakupo's pronunciation of the word "vowels", sings the secret opening to Vanguard Bandits (which is one big fart joke), Big-Al talks about The Problem with Licensed Games (directly quoting Strong Bad), and Lapis deliberately making Big Al freak out even more.
And from the same producer, a somewhat related video featuring the introductions of Yohioloid and Miku English, where Yohioloid takes exception at Avanna mispronouncing his name, then he makes fun of Miku's accent, the Kagamines freak out at Miku English's new design, and Luka gets frustrated that Miku can now pronounce "Road Roller" better than her.
The Twelve Days of Christmas, Vocaloid-style. Special mention goes to Leon being chased by the three French hens and a goose laying an egg in Gakupo's hair.
Triple Baka, sung by Miku with Teto backing her up. Neru is texting in the background, occasionally whacking Miku upside the head with a leek. In this song, Miku gets lured into her little world on the computer and falls asleep at the monitor. She wakes up realizing she has no life. It's hard for her to stop playing around online when the internet is so amazing, like an unknown world she has to explore. Miku gets so obsessed that she doesn't have enough time for doing normal things like laughing, crying, or being angry. The rest just explains how she has given up on everything, nothing matters, and her life sucks. Oh yeah, and she calls herself stupid a few times
Miku's cover of the Chinese folk song TanTe, whose "lyrics" are in fact pure gibberish. Apparently the original was meant to be funny as shown in this video where the singer makes all kinds of silly facial expressions while singing.
Miku's Golden Juice ranges in its humor from gut busting to... rather disturbing, but if you can get past the adult content, it's actually somewhat worth watching, especially Big Al's cameo.
Len hilariously wanting anybody to go out with him.
While it occurs at a crucial moment, Len's shout of "JESUS, JESUS!" in Bad End Night is hilariously narmtastic, especially with how loud and high-pitched it is.
This cover of One Direction's "What Makes You Beautiful" by nearly all the male vocaloids - the MMD rendered PV shows all kinds of hilarious antics, including a scene where the male vocaloids are lying on the stomachs singing, right behind the female vocaloids so that the former are looking up the latter's skirts (and the latter are not amused).