Two, but they have to be very small.
Elf and safety
Legolas
none. That's a hardware problem but have you tried turning it on and off again
One, but the lightbulb has to WANT to change.
One to over hype the new lightbulb and one to make sure it breaks within a year.
One. No, two! No, four! No, eight! No, sixteen! No, thirty-two! ...