Sega TV claimed to be the first "interactive channel", and was generally meant to be loud and abnoxious to counteract Nintendo's quite pedestrian marketing campaign in this region. It is possible that it was inspired by the 1987 Max Headroom broadcast signal intrusion, perhaps the most famous attempt at hijacking a television channel for a short period of time.
Sega TV's "mascot" was the "Sega Pirate", who was seen in many television advertisements, as well as in European promotional videos and occasionally in magazines. There was a limited edition Sega Game Gear bundle with Sega Pirate branding, and it appears on the cover of Sega Ages: Volume 1 for the Sega Saturn.
Both the Sega TV and the Sega Pirate were axed when the company's focus shifted to the Sega Saturn.
(one day Sega Retro should probably host the whole set)