"Better Call Saul" is based around the early years of Breaking Bad's sleazy lawyer Saul Goodman (Bob Odenkirk), as he was climbing the ladder of success.
Fans have long clamoured for a cameo from Cranston as drug kingpin Walter White, even though the two characters seemingly never met before the events of "Breaking Bad".
Gilligan said he remains convinced that an appearance from Walter White in "Better Call Saul" should happen.
"It would be great to see Walter White on 'Better Call Saul'," the writer said.
Cranston has indicated in the past that he is open to reprising his iconic role as Walter White, and will even be directing a season two episode of the "Breaking Bad" spin-off.
His "Breaking Bad" co-star Aaron Paul pranked fans earlier this week with a hoax announcement of his own spin-off.
