Well, since you left a lot of information out, I can only answer in the most general way:
--If your source footage is DV, then you can't zoom in on clips (well, no more than 110% or so) w/o them getting pixellated. DV footage is 720x480 at 72dpi.
--If you have other sources (like still pictures that you've scanned in), try digitizing them at a higher resolution (like scanning them in at 300dpi). That way you can zoom in and not have them get pixellated.
--You should know that what you see on the computer monitor when editing in FCP is not a direct representation of what you'll see on a TV for the final product.
More information would help (i.e., WTF does "pixely kinda" mean?)
MM