The Gag features Homer watching the super-bowl surrounded by snacks. Bart Sneaks in and steals Homer's beer before throwing it onto the power lines outside. After noticing they are gone, Homer runs outside and climbs the tree in the garden to retrieve his drinks only to get electrocuted in the process causing a city-wide power outage.
This couch gag was originally a Channel 4 (UK) Ident used before an airing of the nightly Simpsons episode at 6pm. The gag was commissioned by C4 and animated by Gracie films. Originally the power outage formed the C4 logo which can still be seen in the aerial shot of Springfield.
When Bart refuses to give Nelson a Valentine's card in class, all the class back away and you can see Willie behind the teacher's desk.