Arnold is sick and tired of everybody performing their April Fools jokes on him (especially Helga), so he tries one of his own, but it backfires when it temporarily blinds Helga.
Home video releases
Hey Arnold!: Season 5
Hey Arnold!: The Final Season
Hey Arnold!: The Complete Series
This episode and "The Journal" were produced as three extra episodes to fill in the gap left when the planned 3-part episode "Arnold Saves the Neighborhood" ended up becoming Hey Arnold!: The Movie. As such, this episode and "The Journal" are the only episodes that take place after the movie (despite this episode airing before the movie's release).