From Homestar Runner Wiki
Fthoom-Bang Brand Bottle Rockets is a brand of fireworks that Strong Bad uses for villainous purposes (usually mistaking them for explosives). In Strong Bad is in Jail Cartoon, he tried to break into Bubs' Concession Stand by blowing open the back door with them. This effort was unsuccessful, as The Cheat forgot to remove the "Fthoom" and the fireworks shot up into the night sky, alerting Homestar Runner and the rest of the local police. In Date Nite, he tried to ruin Marzipan and The Cheat's date by shooting the rockets at them from the USS Flirtini, but this too failed, as the rockets propelled the submarine backwards while the fireworks again shot up.