The 2000s, 8: Across The...
When Classics was launched, it was a stopgap that came two years too late for the 20th anniversary and had a modest scope. (To be fair, prior to this the brand had gotten a lot of nostalgic love that also gave longtime collectors some toy features they appreciated, in the Masterpiece and Alternators ranges.) However, the year after that, the movie forever changed the way the brand existed and operated, and essentially gave it enough f-you money to explore doing this nostalgia line stuff more consistently at regular retail, continuing the brand team's conception of what "G1 with knees" meant (which typically included more changes than just knees).
Universe 2.0 (really just called Universe at retail) was a sort of hybrid of Classics and the Movie, taking the brand backward and forward at the same time in ways that weren't always congruous or compatible, but made for interesting and novel toys. By now Hasbro had kind of gotten this era's packaging approach on lock, and approached the line with a lot of packaging design touches that would maintain what Classics started (and cement some that would go on to later Generations lines).
Universe 2.0 responded to the craving for more Transformers product at retail and the hype of the upcoming 25th anniversary (which was incorporated into the packaging). This led to the line covering basically every price point, from Legends to, well, Unicron, with many multipacks besides.
Carded figures would have a red card with a notch cut into the left edge (the red vignetted and fading into shadows on the ends). The classic grid was brought back as a circular grid of radiating lines and concentric circles, forming a sort of wireframe tunnel, reminiscent of some of the G2 packaging but in warmer colors. The line logo was the classic-font Trans Formers on two lines, with "Universe" in glowing text below and backed by a glowing horizontal line ("Robots in Disguise" would appear elsewhere on this packaging). Beveled, colored faction symbols would be in a corner (or next to the nameplates, on boxed figures). Character names were written in white on gunmetal nameplates, and toys would typically be packed in altmode. These elements would more or less form the basis of all nostalgia-themed lines going forward from Transformers (Reveal the Shield) to Generations onward.
Later waves would get a foil label on the corner of the packaging, denoting that this was celebrating "25 Years" of the brand. The packaging design would also use the familiar grungy distressed metal panels for borders and the front card. Rows of cutouts (through which glowed more red) would fill out the bottom edge as needed, sometimes with "Robots in Disguise" written there as well.

One feature from these panels I've never been able to get out of my mind, and am somewhat annoyed by to this day, is the weird swooping curved vent... thing, that formed a corner of the packaging. This would be even bigger on boxed packaging, and was prominent on the front of the packaging throughout. I don't know what it is, it just seems like a weird shape and a bad idea for a way to fill out a right angle.
Far more notorious to normal people was the character artwork. Universe 2.0 was known, perhaps infamous, for its static depictions of characters in robot mode. The intention was to be iconic, stoic, and statue-like, and they certainly were... statue-like. The intended stoic vibe ended up being more Dull Surprise in practice, although Hasbro would try to course-correct with subtle changes like different facial expressions, raised fists, and so on. These half-body shots would be used for Deluxes and up (not counting multipacks). On the right side of the packaging would be a vertical plate listing the faction in colored text.
Boxed figures had the same red backdrop texture, nameplate, and logo design, but would bring one of the more complex box shapes to this point. These were like some weird kind of stretched-out serif D, with a notch on the left and a corner cut on the top right. The side panels would be used for co-sells and character artwork.
The back of the box would feature the by-now-standard-again bio and tech specs, as well as stock photos of the toy in each mode with the relevant callouts.
For the 25th anniversary, Universe figures would also receive a timeline notation on the back highlighting the era represented by the toy: Generation 1, Generation 2, the Beast Era, and the now-formally-named Unicron Trilogy. This was paired with the foil corner on the front mentioned earlier.
Universe was everything you could imagine a Classics line (unnecessarily) crossed with movie aesthetics (some releases more than others) on a movie-toyline budget would be. Toys were sometimes odd blends of both aesthetics, pushing the Classics-level updating of designs even further, and the line was frankly obese with ancillary releases. Hasbro has never been a slouch at making hay while the sun shines, and the sun was going bonkers. The line was a wild mix of new molds (representing G1 and some other series like Beast Wars and Armada), and Cybertron (and other) molds redecoed into everyone Hasbro thought they could get away with (especially given the line's sometime commitment to movie-ish realism).