There are a few limitations regarding alternate characters here on Heroes MUSH.
There is an overall limit of FIVE unrestricted alts per person. (Please see news idlenuke as well.) After the fifth alt, a +request must be sent to gain permission for further alts. Restrictions will be handled on a case-by-case basis after the fifth alt.
Each player is allotted three unrestricted powered characters — that is, three characters who are "evolved" — in general. After the third, players should +request to be allowed to app another.
Alts cannot be related to one another or run into other forms of alt conflict. In no scenario can you play them both in the same scene, or have one alt purposefully, directly benefit the other.
You must wait two weeks in between creating characters. However, you must wait a mimimum of four weeks in between creating your Evolved characters. Nonpowered alts are always a two week wait— so if you create an Evolved character, you can create a nonpowered alt two weeks after that. However, you would have to wait at least another two weeks before being able to create another character. Even if you created a nonpowered alt three weeks after creating an Evolved character, you would still have to wait an additional two weeks before being able to create another character (even though only a week has to pass to create another Evolved character.) If there's any confusion, don't be afraid to page or drop a +request to staff!
"Supporting Characters" don't follow the same rules as Primary Alts. Their name explains their purpose: support! They exist to help other characters with their plots, and as such, are usually directly connected to another PC somehow: the best friend, boss, co-worker, parent, etc. They're there to promote RP without being the main "star" with a role that fits between a main PC and an NPC; not quite the star, not quite the background. (If you need help deciding what should be a Support and what should be an NPC you play, ask staff!)
These support PCs are typically unpowered. However, powered Supporting Characters are possible temporarily by +request — again, for plot purposes, in the case of, say, a villain whose story begins and ends within the span of a plot. There's no set timeframe on these powered Supports, but it is understood that they do have an expiration date of SOME kind at the end of their plot, at which point they'll die or otherwise fade into the background (or sunset, perhaps on a horse).
A shorter, simpler app is required for a Supporting Character: a basic background, +finger, and they're good to go. If they're a temporary, powered Support, they do, however, require a normal power write-up and stunts. The wait between app times is not required of them (just make sure you only have one app in the queue at any given time). You must have a normal PC before applying for a Supporting.
Players are allowed a maximum of two Supporting Characters!