how the hell do you even get 4000 ap
Fed Veigar and a 3 hour long game + Deathcap + Archangels + Soulstealer + Rod of Ages + Zhonyas + DFG
Assuming you can farm like diamond players who get ~300 cs every 30 minutes, and get over 60 kills, whilst last hitting them all with your level 5 Q.
Or:
Deathcap and 5 archangels before they got patched.
Pretty easy.