It's that age-old question: when a kid goes bad, is it nature or nurture?
Jacen Solo is the son of Han Solo and Leia Organa Solo and is gifted with the ability to communicate with animals. He uses this gift when battling the Yuuzhan Vong: he calls amphistaff serpents to him, and they encircle him to form protective armor.
While his twin sister was stubborn and his younger brother was impetuous, Jacen was always indecisive - he tended to focus his Force abilities inward, making him more empathic - that's why he was able to get along well with animals. It also made him the star of the New Jedi Order books, because his journey from novice to hero had the most dramatic changes. After all, a hero with no change or growth is boring.
Jacen Solo was part of the final series of the Legacy
Collection, along with Shaak Ti and the Spacetrooper. He was due to be released in 2009, but became an exclusive in 2010, instead (amusingly, the series wasn't released until after the mailaway offer advertised on the front of the packaging had expired). The majority of his body was originally used with one of those vintage-carded figures - Bespin Luke Skywalker - but it still looks exactly like what he wore in The New Essential Guide to Characters. He gets new forearms, since his are wrapped tighter than Luke's, and a new belt since he doesn't have a blaster.
Like we said for Jaina, it's not really fair to talk about a "likeness" for someone who doesn't actually exist. If you want to see both Harrison Ford and Carrie Fisher's faces in Jacen's, then sure, you can, but it's not so strong that you'd see it unprompted. He's a basic, good-looking kid with slightly shaggy hair, but at least he looks fairly similar to the Young Jedi Knights covers.
Jacen comes with his green lightsaber,
as well as the amphistaffs (amphistaves?) mentioned in the bio. You'll recall that we already talked about the amphistaff in our review of the Yuuzhan Vong Warrior - it's a lightsaber-resistant serpentine creature that can either be used like a whip or a staff. The figure has multiples, but it's hard to count how many: there's one wrapped around his right forearm, a second complete snake that he can hold in his hand, and then an entire nest of the things curled around his chest and shoulders. Obviously they're all removable, which makes them a fun group of accessories.
This figure was part of a build-a-droid series, so tucked away in the lower corner of his packaging is a bodiless droid head. It belongs to BG-J38, a robot made by insects. No, really: it was manufactured by Roche Hive Mechanical Apparatus Design and Construction Activity for Those Who Need the Hive's Machines. Accordingly, it's insectoid in appearance, with a pointed face and bulbous compound eyes.
Jacen Solo was created by Timothy Zahn, who, according to Wookiepedia, named him after a friend of his son's: Jasen. Seriously, "Jasen?" Let's hope that's just an egregious typo, and that there really aren't any parents so awful as to name their kid Jason and spell it with an E. The character became one of the major players in the Star Wars story, so getting a toy of him - even in his younger days - is great!