This blue tee has a bit of an odd mix.
It uses 5 modern character styles, but has the number "91" quite large in the background. 1991, of course the year Sonic got started...but usually when merchandise brings it up, it uses only Sonic himself, or, classic characters only. It doesn't look bad or anything, it's just an unusual thing to do.
Eggman is large in the background, Tails holding a tail, Sonic thumbs up, Shadow 3 point landing, and fist-out Knuckles are in the front, standing on....a blue line. But look...they didn't align the characters' feet quite right either, Knuckles' shoe-bottoms are below the line, Shadow has his fingers below it too, but Sonic & Tails are fairly right on it. It's a colorful tee with a nice selection of characters, just it's presentation is a little bit strange. This is on Amazon (probably) in summer 2019
This is an adults sizes only modern tee.
It has an interesting modern-style look, in all black and white. Sonic is on a rectangle of angled lines with the 'jumping twist' stock art pose. It has his name in pixel type font at the top, and then at the bottom it spells it out in Japanese in a regular block font with some small arrowheads.
The lines make it a little bit busy with the pixel font, but the over-all look is new and fresh. You can tell it's pretty big too, because of how long the torso portion of the shirt is. It's branded with that 'Sonic' only logo stamp thing in the back of the collar. This should be an Amazon item in summer 2019
Photo & owned by Katie
This is a tee that's an Old Navy store exclusive in spring/summer 2019.
It's reddish orange, and is in adults/mens' sizes only, so it should fit everyone. It's kind of an odd combination though, because it uses Modern Sonic, but then mixes him with a very 1970s style thick font & text layout. (The 'the' is sideways as was the fad at the time) They also use the (over-used) faux-wear or 'weathering' to scrape away part of the design to make the shirt look old and used, as if it too, could be from the 70s.
This overly-old-style styling is generally only done with classic Sonic because he fits in a little more with the era and they're trying to promote 90s nostalgia with him. However, the mix of new vs old is unusual and interesting to look at.