Zathras says Sheridan is 'lost in time', Sheridan immediately chimes in 'and lost in S...' but Zathras immediately cuts him off 'Do not say, even now many issues with copyright'. A couple of minutes later when summarising Zathras says 'not only is The One unstuck in time, and the thing... we cannot mention'. This is referencing the TV series Lost in Space (1965).
Zathras tells John Sheridan that Delenn will "never give up, never surrender" in her search for him, a clear wink at the catch phrase used in Galaxy Quest (1999).
At one point Zarthras says Sheridan is lost in time and then he stops Sheridan from saying lost in space for legal reasons. This not only reference, almost, the show Lost in Space (1965) but, "Lost in time and lost in space," is also a line/lyric from The Rocky Horror Picture Show (1975).
At the end, Young John Sheridan walks alongside Delenn through Babylon 5 and meets various characters. Delenn appears in her pre chrysalis version. The first time he saw her in series was after she left the chrysalis. She had hair. Might be a different time line.