Burns: [overcome with emotion] I love you, Smithers.

Burns: [overcome with emotion] I love you, Smithers.
Smithers: The feeling is more than mutual, sir.
-- "The Telltale Head"

Related:

• Burns: Honestly, Smithers, I don't know why Harvard even bothers to show up.
  They barely even won. Smithers: Their cheating was...
• Smithers: Would you feel more comfortable if I left,
  too, sir? Burns: Of course not, Smithers. You're...
• Smithers: Good morning, sir. Care for some coffee?
  Burns: [joyful] No, the promise of a new day is more...
• Burns: Good Lord, Smithers! You look atrocious. I thought I told you to take a vacation.
  Homer: Uh, Smithers already left, sir. I'm his replacement...
• Burns: You should've seen the murderous glint in his eyes,
  Smithers. And his breath reeked of beer and pretzeled...
• Burns: How does he do it, Smithers? Smithers: He's a love machine,
  sir. -- "Homer's Night...
• Burns: Smithers, I've been thinking. Is it wrong to cheat to win a million-dollar bet?
  Smithers: Yes, sir. Burns: Let me rephrase that...
• Burns: Heh heh, look, Smithers -- a creature of pure malevolence.
  He's the perfect one to suckle at my proverbial...
• Burns: [gasps at his sight] Good Lord, Smithers, you look atrocious.
  I thought I told you to take a vacation. Homer...