How do you imagine Wario and Waluigi being introduced in the Mario movieverse?
Running from the cops.
Waluigi is clutching a trophy while Wario has a big bag of cash slung over his shoulder, and they're loudly arguing with each other about whose at fault for their current predicament. It can be quickly surmised that they cheated in some sort of competition, and when their scheme fell apart they decided to just steal the award and the cash prize and make a run for it.
They eventually escape, but amidst the high-octane japes of the chase they lose the trophy and the cash. As a result the two are on the verge of strangling each other once they're finally safe in Wario's hideout.
Wario starts trying to plan their next move. Waluigi desperately wants to bail on this entire stupid "partnership," but Wario reminds him that they're both in too deep at this point, and as much as he would like to never see Waluigi's ugly mug again they they need to watch each others' backs until this whole mess blows over.
"What we're needin' are aliases," Wario muses while his partner sulks in the corner, turning on an old staticky TV to news coverage of their cheating-scheme-turned-heist. "Somethin' friendly an' unassuming, somethin' people are gonna' trust on instinct."
"In other news, The Super Mario Brothers– a pluming / hero duo from The Mushroom Kingdom– prevented disaster today when some of Bowser's remaining troops..."
Wario's attention is steadily drawn to the TV, where Mario and Luigi are shown waving to a surrounding crowd. Wario looks at his and Waluigi's reflection in dirty window, then back at the TV. The similarities are not lost on him, and he smiles a sly smile.
"Hold on, I think I got an idea."
(Note: Neither Wario nor Waluigi refer to each other by name during this entire sequence, so it's implied the names we currently know them as are part of their alias.
They also don't have their copycat-outfits on or the backward L / W emblems. Instead, Wario is in his biker outfit while Waluigi's wears what he had on in Mario Golf : Super Rush.)
