I remember that they all thought Nasty Nick was a C4 plant.
When interviewed by Davina, she asked him if he was a plant for Channel 4
He replied "No Channel 5"
The look on Davina's face for the brief moment before Nick said he was joking was priceless

Marco is trying to be another Brian.
Brian won BB2 and Marco seems to think by emulating him, then he will win.
plain and simple as that.
As for Kitten she just wants to show abject contraryness.
Remember Occam's Razor