Becoming a Clichémagus
Or an Anicliché! Never mind, I suppose it isn't clever either way around. Still, I think it gives you a good idea of what this subject is about.
I don't think any Animagus cliché is the worst thing to hit fan fiction (no, the Draco/Hermione pairing claims that honour *onlyjokingpleasedon'thurtme*), but I read Moony, Wormtail, Padfoot and Prongs fan fiction more than anything else, so I see a quite a lot of Animagi clichés. Here they are, nailed down for your viewing displeasure.
Part I: Daft Animagus Forms
The books are set in Britain. What creatures can you hope to see roaming in Britain? Starlings. Pigeons. Squirrels (some grey, some red). Cats and dogs. Ducks. Badgers. Hares. Chavs. What you will seldom find are lions, tigers or pumas. Okay, maybe the odd puma, but that doesn't count. We know that an Animagus becomes an animal that represents his or her personality. There must be an equivalent to every animal in every country, so I'm not sure how likely it is that the only animal that can possibly represent your character is the snow leopard. Symbolism isn't an exact science. The point I'm trying to make is that, ideally, it would be better for your character to become a native animal. The imagery is just less silly. On top of which, there's no shame in allowing a character to become something small or undramatic. Big cats are so clichéd.
Also keep in mind that it's not canon (at least not so far) that a person's Animagus form can be a magical beast. Phoenix and unicorn Animagi are clichés until proven innocent.
Part II: Animagus Forms Not Being Like What They Oughta
No. No, your character's Animagus alter ego may not be a pink weasel with yellow polka dots. Nor may your Animagus have telepathic powers when she transforms into a trout. Those aren't clichés, fair enough, but some of the Animagi of fan fiction make me wonder if Mother Nature has taken decorating tips from Laurence Llewlyn-Bowen.
Part III: If It Looks Like a Human and Quacks Like a Human...
Another cliché is an Animagus having mystical animal senses when in human form. Actually, I might just be imagining that I've ever read this. It's a cliché on general principles, not because it necessarily exists.
Part IV: Animagi Are Rare, Damnit
It is supposed to be very difficult to become an Animagus (see Part V). This means that it isn't likely that three out of every five wizards in a room will be Animagi (er... Peter, McGonagall and Rita, will you step out of the room for a moment?). It's believable that there would be more unregistered Animagi out there (because when you have a disguise you might not want people to know about it) but I think I speak for many fans when I say that I don't want to read about them. J. K. Rowling only managed to effectively pull it off with Rita because we weren't expecting another Animagus again so soon. It's been done now.
Part V: Becoming an Animagus
The process of becoming an Animagus is unknown, but we do know it's complicated. I've read fan fiction (more than once actually) in which the only requirement was a potion that took a long time to brew. Hell, if it was as easy as making a cup of tea, everybody would do it. If you're going to write about how Wormtail, Padfoot and Prongs became Animagi, please don't be half-arsed and fall into the same old clichés. If you apply some original thought, it could be an interesting part of your story.
I don't think any Animagus cliché is the worst thing to hit fan fiction (no, the Draco/Hermione pairing claims that honour *onlyjokingpleasedon'thurtme*), but I read Moony, Wormtail, Padfoot and Prongs fan fiction more than anything else, so I see a quite a lot of Animagi clichés. Here they are, nailed down for your viewing displeasure.
Part I: Daft Animagus Forms
The books are set in Britain. What creatures can you hope to see roaming in Britain? Starlings. Pigeons. Squirrels (some grey, some red). Cats and dogs. Ducks. Badgers. Hares. Chavs. What you will seldom find are lions, tigers or pumas. Okay, maybe the odd puma, but that doesn't count. We know that an Animagus becomes an animal that represents his or her personality. There must be an equivalent to every animal in every country, so I'm not sure how likely it is that the only animal that can possibly represent your character is the snow leopard. Symbolism isn't an exact science. The point I'm trying to make is that, ideally, it would be better for your character to become a native animal. The imagery is just less silly. On top of which, there's no shame in allowing a character to become something small or undramatic. Big cats are so clichéd.
Also keep in mind that it's not canon (at least not so far) that a person's Animagus form can be a magical beast. Phoenix and unicorn Animagi are clichés until proven innocent.
Part II: Animagus Forms Not Being Like What They Oughta
No. No, your character's Animagus alter ego may not be a pink weasel with yellow polka dots. Nor may your Animagus have telepathic powers when she transforms into a trout. Those aren't clichés, fair enough, but some of the Animagi of fan fiction make me wonder if Mother Nature has taken decorating tips from Laurence Llewlyn-Bowen.
Part III: If It Looks Like a Human and Quacks Like a Human...
Another cliché is an Animagus having mystical animal senses when in human form. Actually, I might just be imagining that I've ever read this. It's a cliché on general principles, not because it necessarily exists.
Part IV: Animagi Are Rare, Damnit
It is supposed to be very difficult to become an Animagus (see Part V). This means that it isn't likely that three out of every five wizards in a room will be Animagi (er... Peter, McGonagall and Rita, will you step out of the room for a moment?). It's believable that there would be more unregistered Animagi out there (because when you have a disguise you might not want people to know about it) but I think I speak for many fans when I say that I don't want to read about them. J. K. Rowling only managed to effectively pull it off with Rita because we weren't expecting another Animagus again so soon. It's been done now.
Part V: Becoming an Animagus
The process of becoming an Animagus is unknown, but we do know it's complicated. I've read fan fiction (more than once actually) in which the only requirement was a potion that took a long time to brew. Hell, if it was as easy as making a cup of tea, everybody would do it. If you're going to write about how Wormtail, Padfoot and Prongs became Animagi, please don't be half-arsed and fall into the same old clichés. If you apply some original thought, it could be an interesting part of your story.