There was one E+B sketch in which Ernie was uncharacteristically malevolent, at least in words.
It was when Ernie was about to show Bert his ice cube collection. Ernie found these beautiful ice cubes, but they were freezing cold. So, Ernie took the ice cubes, put them in a box, and put the box under an electric blanket. Bert asked Ernie if he could see them, knowing full well what the outcome would be. Ernie is shocked to find that the ice cubes had been stolen. When Bert points out that there's water in the box, Ernie takes that as evidence that a fish stole the ice cubes. Finally, Bert explains what happens to ice cubes when you take them out of the fridge. Ernie then concludes that a fish melted his ice cubes.
"AND WHEN I CATCH THAT FISH, I'LL TEAR HIM FIN FROM FIN! Oh wait till I get hold of him!"
Bert bemusedly adds "Go get 'em, Ernie."