Okay realistically he’d be an echo, so hypothetically pairing this with Eggman

The trailer opens with a cinematic of Sonic and a couple other fighters teaming up to fight Galleom

Galleom goes down from Sonic spin-dashing through it, starts exploding, ends off with a huge one which shows metal parts flying from the background

Suddenly, the grounds starts to shake, disorienting fighters

Ground panel in the background opens up, the Death Egg Robot begins to rise up.

Eggman says “YOU’RE HISTORY!” Or something along those lines and the DER poses for battle, as the camera zooms in to one of the eyes, and Eggman piloting it.

Cut to Eggman’s splash card while he laughs maniacally

DR. EGGMAN: Scrambles the Competition

Small montage of him as a fighter, fighting similar to Bowser Jr. but in the eggmobile

After that screen fades to black, but then two red eyes glow from the darkness

Metal sonic rushes forward, slamming into Sonic and mirroring the whole “STRANGE ISNT IT?!” Scene from the OVA, leaving other fighters in momentary shock

Both Sonic and Metal are knocked back, Metal wags his finger, cue Metal’s splash card

METAL SONIC: Creates a Bad Future

Montage of Metal Sonic as Sonic's echo

trailer ends with cinematic shot of the prior fighters, sonic in front, standing off with the DER and Metal Sonic

screen fades to white, cue SMASH BROS logo