Extra Strength was a gag created by Seamus and Sp00n. They said it randomly during their Co-op playthroughs.
Origin[]
During their Gears of War 2 playthrough, a character, Baird, asked if a planned explosion be regular or "extra strength". Sp00n remembered this part and said it before the character, Marcus, said it. After hearing Marcus say it, Seamus was disturbed by the fact of how close it was to Sp00n's one.