Sinclair and Ivanova enter the planet across a walkway in a high-tech abyss. This impressive shot is a direct homage to the similar Krell Machine scene in the 1956 classic and highly influential 'Forbidden Planet'.
Londo's story about marrying the Centauri dancer is consistent with Babylon 5 canon. What he leaves out is the fact that his family forced him to divorce the dancer almost immediately.
Garibaldi asks Talia to see if she can use her Psi-Corps connections to get through to Mars, via a Psi-Corp at Syria Planum. The story of how he knows about that facility is told in issues 5-8 of the Babylon 5 comic book published by DC comics. Garibaldi is heard telling part of this story in Infection (1994) and later says more about it in Messages from Earth (1996).
This takes place in June 2258.