Hayate the Combat Butler!! (TV)

On episode 3 at 5:20, the flower that they need to collect (Celcetta Flower) comes from Y's II

At 7:30 on episode 3, the show goes into "The World" (but it's normally called Za Warudo as that's the romaji for it), which is Dio's stand in Jojo's Bizarre Adventure. The stand had the ability to pause time for 5 seconds (which is a bit less than what the episode pauses it though).

On the episode 4 preview, Nagi is describing Dhalsim of Street Fighter II fame (Yoga allows you to stretch your limbs, teleport and fly in the air... finally, Hayate Inferno, his super)

At 19:10 on episode 2, Katsura calls herself Deedlit Yukiji, Deedlit was the main heroine of Record of the Lodoss War, a 90s anime.

The title of episode 12, "Cruel Big Foolish Guy's Thesis", is a reference to Neon Genesis Evangelion's opening track, "Cruel Angels' Thesis".

the title of episode 4 is exactly the same like the ED song of Gundam SEED Destiny, "Kimi wa Boku ni Niteiru"

The title of episode 11 which is "Hinamatsuri no koro ni" seems to be a pun of "Higurashi no Naku koro ni" anime

Episode 13 - around 11:28. Reference to the DVD release VS the broadcast episode orders of 'suzumiya haruhi no yuutsu' is made. The decision to release the DVD episodes in a linear (plot chronological) order caused much unrest among the fan base or fan community of the series, that grew from the original broadcast of the TV anime (that aired in a non-linear order).

In ep 19 around 4:23, Nagi comments "Nagi 360 Elite" most likely in reference to the new ""Xbox 360 Elite" model.

in ep 25, as Hayate was reading a book to Nagi called Alice in Wonderland, the first line Hayate told Nagi is a spoof from the anime Gundam Double O (00).

In episode 1, Maria and Saki interrupt the race by posing as "Black Max Heart" and "White Max Heart." This is a (blatantly obvious) reference to Pretty Cure Max Heart's Cure Black and Cure White. Rie Tanaka (voice of Maria) plays the part of Hikari/Shiny Luminous.

In episode 2, near the beginning where Hayate purchases a yellow wrapped candy bar called Snackers, it is supposed to be a Snicckers, obviously.

In Episode 2, when Sister Fortesia takes down the masked mugger around 8:50~8:55, her glasses are whited out from a source of light and she poses before she says "Amen". This is a reference to Alexander Anderson from Hellsing.

At 10:37 in episode 3, the "River Styx" is the river that separates the earth with the hades in greek mythology.

At 18:06 in episode 3, Katsura appears with the Majin Boo symbol on her forehead.

In episode 3 around 08:06, when Isumi and Hinagiku helped Hayate and Nagi, they said 'toori sugari no seigi no mikata'. It contains the reference to Kamen Rider Decade ('toori sugari no kamen rider', said by the protagonist Kadoya Tsukasa/Kamen Rider Decade) and Kurogane no Linebarrel ('seigi no mikata', said by the protagonist Hayase Kouichi)

In episode 4, at about 04:18 when Nagi mentions mixing demons, it might be a bit far fetched up, though it is likely related to Shin Megami Tensei where the user mix demons together to obtain a new demon with another form.

In episode 5, starting at around 06:10, in the background you can several look alike movie posters that appear to be Indiana Jones, Blade Runner, Aliens, and Saving Private Ryan.

In episode 5, at about 11:32 the three villains are rough cameos of Street Fighter characters from left to right, Rufus, Zangief and Guile.

In Episode 8 at around 3:36,When the seed breaks in Nagi's eye, it is a parody of Gundam Seed when a seed breaks in Kira,Athrun, and Cagalli's eyes.

In episode 9, right around when the sister is walking out of the video store (at 11:02), above the shelf of videos there's a movie poster for Indiana Jones and the Temple of Doom with an inverted image.

In episode 10 around 13.30, you can see a girl that resembles Arashi of the Natsu no Arashi series, which happens to be the same seiyuu as Hayate.

In Episode 10, when Maria runs out of the room (18:50), you can clearly see there's a room behind the doorway. However, when she reopens the door (20:02), it leads outside.

In episode 10, at 18:36, the outfit Tama is wearing is a reference to Johannes Krauser II from Detroit Metal City.

In episode 12 at around 7:50 when the SPs are fumbling over Nagi's kidnapping, one of them says that "A Super Soldier (Chouhei) can't win against an Innovator". This is reference to Kidou Senshi Gundam 00.

In episode 12, Hinagiku sings "Cruel Angels' Thesis," Neon Genesis Evangelion's opening song, at her birthday party. Some of the movements and poses she makes as she sings, as well as some of the "camera" angles, are also taken directly from Evangelion's opening sequence.

In episode 15, at about 6:50, 66a can be seen on the clock being a reference to 666 Satan by Seishi Kishimoto since the sixes are of a similar style.

In episode 18, near the beginning, when Hayate asks Nagi what she wants, she says she wants a drill, because it would be the first thing she would put on her robot. This is a reference to the anime Tengen Toppa Gurren Lagann, where the main hero's mecha's weapon is a drill. Hayate then ask why she isn't at school, and Nagi just ignores him and says that if she has a drill, the robot would be able to move; this is, more specifically, referencing the Core Drill and how it activates the Lagann in the first episode of TTGL.

In episode 19 at 20:31 when Hayate hugs Maria, the hammer Nagi hits him with is Graf Eisen, the weapon used by the Velka Knight Vita in Magical Girl Lyrical Nanoha A's

In episode 19, the opening typewriter sequence is a parody of Lupin III TV in which each episode title is done this way and ends with a gun bullet sound. Also, at around 15:04 there is some updated movie posters of Caroline, Terminator: Salvation and Transformers 2. On the DVD rack you can see as it appears to be Blade Runner, Independence Day, and Hellraiser.

In episode 19, at about 6:30 signs can be seen in the background reading "Hard Bank" this is simply a pun on the opposite of "SoftBank" one of the most popular cellphone service provider.

In episode 19, at about 18:20, Maria is humming the song Fly High from the anime Gunbuster or Top wo nerae.

In episode 19, fans of Yu-Gi-Oh will recognize the card game imitation that appears right before the commercial break, including the nearly always-used phrase "Ore/Watashi no turn. Draw!". There's even a reenactment of the end of Yami's second duel against Insector Haga involving drawing monster cards indefinitely to cause unnecessary attacks.

In episode 20, Nagi plays a game that can be thought as a Dragon Quest(DQ) game because the fight screen is similar and she encounters "Prime" which is obviously supposed to be Slime in DQ, she even fights a King Prime, which is also known as a King Slime.

In Episode 22 around 11:36, Kyobashi Animation created "I'm just simply Melancholy". That's the title parody of "The Melancholy of Haruhi Suzumiya". It is produced by the animation studio of Kyoto Animation. And Shitsubou Sensei is the title parody of Sayonara, Zetsubou-Sensei

In episode 22, around 8:39, Nagi talks about a hamster (Nagi's name for Nishizawa) with ambitions to become Paris' Top Chef and that it will only attract pets and not a movie deal. This is a reference to the movie Ratatouille where a rat becomes a top chef in Paris

In Episode 23, the title of the episode "Bokutachi no Yukue" is the third opening song title of Gundam Seed Destiny sung by Hitomi Takahashi.

In episode 23, Wataru is forced to do something on a stage for Sakuya. What he does initially begins to shock the audience because he mimics Ryu's hadou-ken movement from Street Fighter II V.

In Episode 25. At about 5:53. There's a background of Celestial Being similar to the beginning of the story of Mobile Suit Gundam 00

In Episode 25. At around 9:06. Nagi wants to buy "Packy". Instead of the word "Packy" the word is Pocky. Pocky is a chocolate stick that has been popular in Japan. It has been produced by Ezaki Glico foods from Japan.

In episode 25, when Hayate was showing Nagi a video of a girl dancing, there are two parodies shown at the same time. First is the dance, which is the infamous Caramelldansen. The second is that the girl resembles Hatsune Miku with the tie, ponytail, short skirt and ribbons. This is further shown by the name if the video starting with "Mikumiku"

In episode 25 when hayate was hit by a truck and got saved by the football he was holding, it's referring to captain tsubasa. He was also hit by a truck and got saved by the football he was holding to.