The unusual thing about this particular invasion is that it paradoxically both did and didn't happen. That is to say, unlike its contemporaries on this list, DX's supposed 'siege' of rival promotion WCW in April 1998 was for realsies - and as a consequence, led to absolutely nothing tangible besides interest from the local police in Hampton, Virginia.
Whilst WCW's flagship show Nitro emanated from nearby Norfolk, Triple H and his DX cronies hopped into an apparent 'tank' - actually a 4x4 with a turret strapped to the trunk - and brought their brand of banterific antics to the company's backyard. Manning a megaphone, the renegade group's equine leader shouted to the gathering crowd outside the arena such trenchant quips as "WCW sucks", before the quintet attempted to make their ingress.
Ultimately, they were thwarted; refusing to rise to the bait, WCW slammed the door shut on DX's 'tank', and that was the end of the 'invasion'. Not a single wrestling match arose from the stunt, but the (pretend) shots fired nevertheless left DX's mark on the wrestling map. WWE were the cool rebellion worth supporting; their rivals were mere cowards.