I generally refer to this...
...as an "intergalactic, cross-series woo", for exactly this reason =)
( Professor Kenny Martin Receiver of the world's first Marbleositing, Fri 28 Sep 2007, 9:24, archived)

it's that darn rip in the space/time contimuium that does it.
'Ningles.
( Thor_sonofodin https://twitter.com/Thor_sonofodin, Fri 28 Sep 2007, 9:33, archived)