When Walter and Skyler visit the lawyer, the scene cuts to a shot that displays a Master of Arts degree from the University of American Samoa presented to Saul Goodman. In the prequel series Better Call Saul (2015) it is revealed that a law degree was earned by Saul who at the time still went by his real name, James McGill, but Jimmy got his law license suspended in BCS. When he was reinstated he practiced law under the name Saul Goodman and had his paperwork changed to reflect that.
In the flashback scene of Jesse and Jane visiting the Georgia O'Keeffe Museum, when Jesse implies that Jane is perfect, Jane says, "Aww, that was so sweet! I think I threw up in my mouth a little bit." That was exactly how she died.
Tomás tells Jesse to "bounce" (meaning go away), exactly what Combo told the kid to do before he was killed.
When Saul and Walt are discussing the car wash as a plausible cover, Saul says at one time he convinced a woman he was Kevin
Costner, which is exactly what he did in BETTER CALL SAUL.
When Walter walks into Gus Fring's house after being invited to dinner by Gus, there are some children's toys and a small children's table. Walter obviously notices these things. But there is never any further discussion about Gus having any kids or if he was ever married, etc.