There are a few small (and I do mean small) studies out there that claim to demonstrate some benefit in bipolar disorder for patients who were non-responders to lithium and depakote, mostly in reduction of manic symptoms. This is the most interesting one:
Donepezil in treatment-resistant bipolar disorder - ScienceDirect . It seems like not an absolutely insane third or fourth-line treatment approach for the sort of bipolar folks who have been depressed like once ever and mostly get manic on a very regular basis. Probably not at all useful for the sort of bipolar folks who got hypomanic/manic like once ever and mostly get depressed on a very regular basis. Can't find any similar data for aricept.
So basically either the person prescribing this is someone with a very deep knowledge of essentially speculative approaches to managing treatment-resistant bipolar disorder, or they are a muppet as whopper suggests.