(This was gonna be a A+B mashup but I learned that the El Horso Project already did this mashup so I just threw a curveball and included another Weezer song :) )
Mashup Includes:
Bowling For Soup - Today is Gonna be A Great Day (Phineas and Ferb Opening Theme)
Weezer - El Scorcho
Weezer - Undone (The Sweater Song)