Wally is not indispensable, he's simply incomprehensible = The Zen of Wally, the one who is there and not there at the same time....the best I can do at meetings is go glassy-eyed and try to keep from banging my head on the table from falling asleep.....
Manager: You should get a cell phone.
Manager: Because you are indispensible. We might need to call you after work or on the weekends.
Me: Then why don't you issue me one?
Manager: You're not THAT indispensible.