Can a graduate student friend of mine help me get into a different grad program at the same school? I have a friend who'll be attending a graduate program in Physics, at a school I would be interested in for when I am applying to grad schools. However, I'm a CS major, so I'd be applying for that.

My question is what can he do that would help at all in making my admission more likely? I know the research he'll be doing is interdisciplinary (Physics and CS) so he'll have some interaction with CS. As a first-year grad student, he won't have much weight, but I'm still curious.
It is highly unlikely that they would have any ability to directly influence your admission to any graduate program. It is plausible that they could help you indirectly, however.  They could be helpful for the following:


Scouting Professors/Labs: Finding out more about the interests and goals of the professors and labs that you would want to work with. This would help you tailor your application so that certain professors might be more likely to advocate for you, if they see a good fit for you in their lab.
Gathering Comparisons: Talking to recent grad students admitted to the program and seeing if they wouldn't mind sharing their application packets, so you could see what a successful candidate looks like (and what factors seem to be valued).
Informal Reference: If a professor who is reviewing your application packet has worked with your friend, they might ask them for some details about you. This is highly unlikely in your case, due to them being a new student and in a different department. I provided this kind of background once when my lab was evaluating an acquaintance of mine from my undergraduate program. It is fairly uncommon and would not sway the decision greatly.


Some of these things would have been more effective if they were performed earlier (e.g, gathering comparison CV's), since it gives you more time to beef up any weak spots that you have or to build on your strengths.