an accomplishment or goal that is ridiculous and crazy; the very accomplishment of said goal requires the creation of several new adjectives to correctly describe it.
Can also be used sarcastically to imply that the subject is making a much bigger deal about an accomplishment than is necessary.
2. I don't know dude. You want me to date your hideously ugly sister? Thats asking me to do a Phelspian Task.
3. Oh, you beat "Creep" on Easy Rock Band drums? My, my. What a Phelpsian Achievement.