"The hardest thing to walk away from is the camraderie of the company," Jackson tells us at the start of the call, echoing the sentiment of co-star John Noble. Jackson, whose Peter Bishop has gone from conman, to would-be savior of two universes, to future freedom fighter will be seeing his character's journey coming to an end in tonight's two-part series finale of "Fringe."

Jackson pointed to the relationship between Walter and Peter and Peter's desire to become a good son as "an interesting journey to go on." He looked back at the character's arc over the last two seasons, which saw Peter pulled from the timeline, hoping to return to his own, ultimately finding love with this universe's Olivia and caring for his father. It was a curious direction for the series to go at the time, kind of a soft reset of his character's arc where he started out as more or less mercenary in his aims and actions at the beginning of the series, and developing connections with Olivia and Walter. A lot of season four was about his character attempting to get back to his universe, no matter the cost. But the Peter in season four wasn't the Peter at the beginning of the series: no longer selfish, he couldn't abandon the people he cared for and made the decision to remain in this timeline.

The actor also spoke about the "Peter-as-observer" arc which crossed part of this season--gripped with anger at the death of his and Olivia's daughter, Peter implants himself with Observer tech, slowly losing his emotional connections in his path for revenge. Jackson saw this as a mirror of Walter's own arc as an "ends justifying the means" scientist--it was only when Peter was in danger of losing his family that Peter was able to turn back. Again, the common theme of this season and Jackson's experience with Peter Bishop is the dramatic evolution of his character. While he didn't have a specific moment to single out as a favorite in the series, Jackson says that the ongoing arc between Walter and Peter as his favorite element of the show.

Looking back at the arcs of his costars John Noble and Anna Torv, Jackson says that for Walter, it's been the fear of becoming the ultimate, complete version of himself (with all of the dangerous hubris that entails). With Olivia, the issue has involved allowing her emotional walls to drop in order to find love and even become a mother (however briefly). Both characters' journeys have been very universal, very human issues amid all of the typical sci-fi mystery and adventure.

On shooting the finale, Jackson compared "Fringe's" end to the "Dawson's Creek" finale nearly 10 years ago, describing both as having a carnival atmosphere where everyone involved gave their all. Jackson says that he has an even more personal stake in "Fringe" given that it's a genre he's particularly passionate about. He went on to talk about how series like "Star Trek" and "Firefly" both had such passionate fanbases because of the scarcity of the shows--their short runs made them more beloved in fans' hearts. For him, "Fringe's" afterlife seemed to begin even as the show was still on the air, and he appreciates the fans' support over the years.

Will Peter survive the finale? Or Walter? Or Olivia? We already know that Walter has a target on his head, a necessary component to the defeat of the Observers, but of course, Jackson's not talking about his or any of the other characters' fates as the series reaches its conclusion. But he does feel that Peter reaches the best possible conclusion, earned over the course over the previous four seasons.

The "Fringe" series finale airs tonight on FOX at 8 PM ET.