Elective organ removal: spleen, tonsils, maybe bile duct (?)

What else could you get away without, I wonder?

Also, what's the name of the doctor who does this kind of work? It's not plastic surgeon.

Then again he is an alien animatron. Do we have to limit this discussion to human beings?

a "general surgeon". Ditto for bile duct, but you can't remove that without serious consequences, you were probably thinking of "gall bladder" (damaging the common bile duct accidentally during gall bladder removal surgery can have catastrophic and even fatal results to the patient). Tonsils are typically removed by an ear, nose and throat surgeon, or otolaryngologist.

There's a lot of tissues that aren't needed to survive. Examples:

Adenoids (near tonsils)
Appendix
Uterus, ovaries (if you don't care about having kids)

etc.

That doesn't mean there aren't consequences. Losing a spleen, even though not strictly speaking necessary for life, can render a patient more susceptible to life threatening bacterial infections.

none worse without it.