How the 25th Amendment Works
 

Section 1: If the President goes belly-up, or cops out completely, the Vice President becomes President.
Section 2: If the Vice President goes belly-up or cops out completely, the President gets to choose who gets to be Vice President, subject to majority vote of both houses of Congress.
Section 3: If the President says to Congress, "Um, hey, guys, I'm not feeling so hot right now", the Vice President gets to be Acting President (not actual President), until the President says, "I'm good now, kthnxbi."
Section 4: If the Vice President and a majority of the heads of the Executive Offices agree the the President is a whackjob, they have to tell Congress this, then the Vice President gets to be Acting President. The President can then say, "Dude! Personal space here!", and he gets to be President again: unless. See, the Vice President then has four days to challenge the President to a mud-wrestling contest; again, with a majority of the heads of the Executive Offices as his cheering session. After this, the Congress has has 21 days to form a big mosh pit-or, if they're not at the punk rock concert, 2 days to get to the concert, then another 21 days to form the mosh pit. If 2/3 of the whole congress support the Vice President, and can out slam-dance the 1/3 of the Congress who support the President, then the Vice President gets to win the Tony Award for Presidency.

I hope this clears things up for those of you who might not be in the know.