Humans Need Aliens

Humans Are Special right? Of course they are. Why else would every alien and magical creature come to Earth?

But then again, aren't humans also Puny Earthlings and mostly Muggles? So how are they to stand up against whatever threat is out there?

Well luckily, for whatever species is threatening the Earth, there's always one member, or another race that opposes Earth's invasion/colonization/whatever and is there to lend a helping hand. Mind you, the alien can also be an angel or some other benevolent supernatural creature.

Fridge Logic sets in as one has to wonder how humanity got on before the alien showed up.

Contrast Muggles Do It Better; for when human technology, usually in an over the top fanfic, can outmatch any supernatural abilities; and Humanity Is Infectious; for where human morals and norms influence the alien society and undo its Space Age Stasis, allowing it to move forward and develop again.

Examples of Humans Need Aliens include:

Anime

• If Saiyan Goku hadn't shown up, you can bet that the Dragon Ball Earth would have gone the way of the Dodo.

Comic Books

• Superman is the Trope Codifier. Without Superman and the threats he stops on a daily basis, humanity would doubtlessly have gone extinct a few times over in The DCU. The same goes for Supergirl but Superman is far more iconic and likely to come to people's minds.

Fanfics

• If it weren't for Superman in The Last Son, Earth would likely be superheated vapor.

Film

• In Bumblebee, the eponymous Autobot is the only one who can stop Shatter and Dropkick from summoning the Decepticon fleet to Earth. Even all of Sector Seven's weapons are useless against the two Decepticons.
• Without Superman, Earth would have become New Krypton in Man of Steel. Admittedly, he also put Earth, albeit unintentionally, in danger in the first place.
• Played for Drama in the Marvel Cinematic Universe. Both the space borne threats in Captain Marvel (the Kree Empire) and Thor (Loki) could only be stopped by the aliens who'd brought them to Earth in the first place. By the time of The Avengers, S.H.I.E.L.D. is taking steps to avert this trope and make way for Muggles Do It Better with Phase II weaponry.

Live-Action TV

• If Superman isn't the Trope Codifier, then Doctor Who certainly is. As much as the Doctor loves humans and waxes on about the "indomitability" of the human spirit, the Earth would be a burnt out husk without him constantly pulling humanity out of the fire. A prime example is "Turn Left", a For Want of a Nail Alternate Universe where the Tenth Doctor died too quickly to regenerate. Within a year, worsening conditions and alien invasions had turned Britain into an irradiated quasi-fascist police state while America had sixty million citizens turned into Adipose.
• In Star Trek: Enterprise, the Vulcans are the ones who pulled humanity out the After the End scenario that World War III left the world in. It's frequently said that without the Vulcans, humanity may never have made it to space.
• Supergirl is quite often the only one who can stop all the horrors, alien or otherwise, that threaten National City.

Video Games

• Inverted in Mass Effect. It's the humans' fighting spirt that rallies the aliens against the Reapers.

Western Animation

• All the citizens of Arcadia-Oaks need Aja, Krel, and Varvatos in 3Below to combat any alien threats. Toby even sics his magical warhammer on an alien Bounty Hunter and it does nothing.
• Though he's a human being, Ben 10 uses powerful alien technology to fight off all the evil aliens threatening Earth and the Plumbers employ Token Human.
• Like Transformers, Challenge of the Go Bots sees humanity dependent on the Guardians for aid. Unlike Transformers, humanity develops a good deal faster thanks to alien intervention.
• In Steven Universe, all life on Earth would have perished if Rose Quartz/Pink Diamond and her Crystal Gems hadn't turned against the colonization effort back in the Bronze Age. Likewise, only the Crystal Gems can stop the Cluster from ripping Earth apart.
• Transformers is all about Earth being the latest battleground for the Autobot/Decepticon war with humanity needing the former's help to survive. How much help humanity needs, and how much it develops, varies greatly from series to series. For example, humanity uses reverse engineered Cybertronian technology to become even more advanced than the Transformers in Beast Wars: Uprising, but other works, like the Transformers Aligned Universe sees humanity be almost terminally stupid and, except when using Cybertronian weaponry, be unable to even scratch a Decepticon.
• Inverted in Voltron: Legendary Defender. Voltron's five pilots are human and all the alien worlds conquered by the Galra Empire need the Humongous Mecha to help them out.