Some early concept designs for the Werehog, from 'Sonic Unleashed'.

'Sonic 4 Episode 1' was released 16 years ago today in the US.

Where did you first play 'Sonic 4: Episode 1'?

In the ‘Sonic 1′ prototype, once Sonic went past the sign post, his jumping action would allow him to pump his fist in the air.

'Mario & Sonic At The Olympic Winter Games' was released on the Nintendo Wii 17 years ago today in the US.

In the Game Gear & Master System versions of 'Sonic Spinball', the bonus stages are oddly egyptian themed.

Head Up Sky Rail 'Sonic Adventure 2'

Get The Keys! Hang Castle Team Chaotix 'Sonic Heroes'

Thanks to CodenameGamma for the camera hack.

In the Graveyard Gig stage of 'Sonic & All-Stars Racing Transformed', many posters can be found outside the Mansion. One of them is a Reservoir Zombies poster, referencing the film 'Reservoir Dogs' .

"I'll find that Eggman!" A comparison of Sonic's model in 'Sonic Adventure' and the DX re-release, from the Battle with Gamma cutscene.

A turnaround of the Tails toy from the 'Sonic Boom' TV series, released by Tomy. This one came with a DVD box set.

Adabat - Night 'Sonic Unleashed' Kenichi Tokoi

Big The Cat wallpaper, released on the Sonic Channel website in June, 2013.

Part of the recent Cartoon Network leaks - the model sheets for Shadamy from 'OK K.O: Let's Be Heroes' - a nod to both Shadow and Amy Rose, and a character obsessed with other people's romances.

'SEGASonic Bros.' - let's talk about it!

Shorty goes nuts! The cover for 'Sonic The Comic' #46, 3rd March 1995.

An early sprite concept of a ‘Sonic 2′ enemy, made by Tom Payne. This Pterodactyl would drop bombs on you.

A closer look at the ghosts from the Wonder Museum track in 'Sonic Racing CrossWorlds'. This one's wearing a cowboy hat.

Turning Corridor Mystic Mansion Team Dark 'Sonic Heroes'