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 summarizing 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), which included a young Bill Mumy in the cast.
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).
The animated format was chosen for several reasons: it makes visual effects somewhat easier and cheaper; it helps to cover up the fact that the returning actors are getting older; and it allows substituting voice actors for actors from the series who have passed away or chose not to return. The replacement actors are: Paul Guyet, who plays Zathras (originally played by Tim Choate, who died in 2004) and Jeffrey Sinclair (originally played by Michael O'Hare, who died in 1998); Anthony Hansen, who plays Michael Garibaldi (originally played by Jerry Doyle, who died in 1998); Phil LaMarr, who plays Dr. Stephen Franklin (originally played by Richard Biggs, who died in 2004); Piotr Michael, who plays David Sheridan (originally played by Rance Howard, who died in 2017) and Marcus Cole (originally played by Jason Carter); Andrew Morgado, who plays G'Kar (originally played by Andreas Katsulas, who died in 2006); and Rebecca Riedy, who plays Delenn (originally played by Mira Furlan, who died in 2021).