In the area that you get Model L from the boss, in the area where you go to find the data disk about the biometal where the reversed L group of ice smash them and you find the boss that you meet in the Dark Elf chase (the water stage one) from Megaman Zero 3 hanging from their foot upside down. Also when you get the password data for Model L in the screenshot it shows Zero and Cell in front of a huge group of mavericks guarding a dome-like building. Also the models are from these Megaman Zero charecters: Model H (Harpiua), Model X (X of course), Model Z (Zero), Model F (Fefnir), Model W[the fragment not the core] (Weil[yes it's odd]), Model P (Phantom), Model O (Omega in Zero's orginal body), and Model L (Leviathan).

If you want model OX,do this:play on normal mode and pass the game,then fight omega,if you win,go to the zone were it asks about those megaman zero 3 and 4,don't go to those doors,instead go to the door to the left,and you will see a mysterious rock,take it fleve and he will give model OX

First becom Px, then start shooting at him rapidly. When he comes your way either jump dash him (if he is on the ground) or dash beneath him (if he did that uppercut thing).