kirby, roz, the boss (6) a what device?

Lana's Kitchen. Kirby is sitting at the table with a textbook. Frasier seems to be grasping at straws in an effort to make Kirby learn anything.

Frasier: The trick remembering the difference between William Henry Harrison and William Howard Taft is a simple mnemonic .
Kirby: A ?
Frasier: It's a trick. Harrison died in after his first month, so we say "William Henry Harrison Was Hardly Healthy". And you can't spell "Taft" without the f-a-t.
Kirby: So now to remember two things, I have to remember two things. Plus the first two things. That's FOUR things.
Frasier: Yes, but the first two things are easier to remember and they are to the second. Will you just try to up, Kirby?

Kirby: What are you all up in my face ?
Frasier: Because you are not working hard .
Kirby: Well, fault is that?
Frasier: Yours.
Kirby: , dude.