Sensible: Rumble x Cotton Cloudy
Crack-like: Rumble x Button Mash
More crack-like: Rumble x Flandre Scarlet
Much more crack-like: Rumble x Milhouse
Sensible: Cotton Cloudy x Rumble
Crack-like: Cotton Cloudy x Zipporwhill
More crack-like: Cotton Cloudy x Cartman
Much more crack-like: Cotton Cloudy x Fin from Phantom Breaker
April Fool!
Seriously, though, Rumble x Cotton Cloudy (though that’s probably a bit too sensible)
Edit: Or Rumble x Babs Seed. Or Cotton Cloudy x Babs Seed