Hi Khaniari,
There is an Add-On for iChat called
ChatFX which does a whole raft of Video tweaks to the Camera input.
Now these are Quartz files that can be opened In Quartz Composer if you have the Developer tools Installed. It is not that difficult to Duplicate one or two of the items they give you to make your own.
You can use something like SnapZProX to record parts of the Screen and play them in Preview of iChat. Of course iChat lets you take any firewire Input such as a DV camcorder playing pre-recorded film.
I have spent some time briefly looking at whether these can be Exported as something iMovie can use but have had no luck yet.
1:35 PM Thursday; June 28, 2007