There's some nice promotional art featuring Sonic and some other characters in the background of the studio.
Also, you may have noticed that Sonic used to have the generic player icon and HP aesthetic in earlier showings of the pack. Well, it has since been updated - his border is the classic emblem logo, and his hearts are now 1-UP monitors.
Also, in each level in LEGO Dimensions, there is a "character in peril" that you have to find and save, and you can see a preview of them on the pause screen. Well, in the Sonic Pack's level, it's actually Big the Cat!
Also they have a really nice Genesis style "Title Screen" intro at the start of the level
When Sonic falls into pits or loses all of his HP, he doesn't "burst" apart like most characters. Instead, he has the classic animation from the Genesis games.
And another really funny tidbit - near the end of the footage, you hear that one of Sonic's generic phrases that he can blurt out is "Hey, long time no see!". It sounds like a random one liner, but it's actually a reference to a lot of the 4Kids era of Sonic voice actors. "Long time no see!" was an INCREDIBLY overused phrase in the English dub of Sonic X and many of the games the 4Kids cast worked on. They really know the fandom well, and are going very in-depth with the references, it seems!
They also mentioned that, while Green Hill Zone's section of the level is 2.5D (with minor background and foreground space to move in and out from), other sections will have different camera perspectives more reminiscent of the 3D games like Adventure, so the different sections of Sonic's level are literally going to be like ripping those levels from their game!
They also mentioned that a lot of the Year 2 packs are twice as big as an individual pack from Year 1. They also said they consider Sonic to be the crown jewel of the Year 2 packs. Which is really nice to hear, it means they are truly going all out with this. I'm honestly as hyped for this as I would be for a new 3D Sonic game!