Sonic the Hedgehog 4 goes episodic this summer - GameSpot

Project Needlemouse revealed as side-scrolling sequel to speedster's original Genesis trilogy; Episode 1 confirmed for Wii, Xbox 360, PS3.
Sonic is back for his fourth installment in the classic 2D series, revamped from the ground up.

Sonic the Hedgehog 4: Episode 1 - Game - Nintendo World Report

Sonic the Hedgehog 4: Episode 1 - Game - Nintendo World Report

Sonic 4 announced in episodic form

Sonic the Hedgehog 4: Episode II (2012) - MobyGames

Sonic the Hedgehog 4: Episode 1 - Game - Nintendo World Report

Sonic the Hedgehog 4: Episode I - Wikipedia

Sonic 4 Legacy - Games - Sonic Stadium

Sonic the Hedgehog 4: Episode I - Wikipedia

The History of Sonic the Hedgehog: The Revival Era - LevelSkip

Hey Sega, why is Sonic 4 episodic? – Destructoid

Sonic the Hedgehog 4: Episode I — Вікіпедія