Reasons I recommend:

A) Never have the first three letters of any stored user procedure be "sp_"

B) Always use three part naming, so you either execute:

Adventureworks.Person.(otherprefix)ReturnSomething

or

Master.dbo.(otherprefix)ReturnSomething

both of which make it explicitly obvious what you're calling.

Ambiguity is a playground of subtle bugs.