Tantrum, real name Tristram, is a character that appears in the Sonic the Comic series published by Fleetway Editions. He is a young mouse from the Metropolis Zone. He is named after his habit of throwing constant tantrums.
Under unknown circumstances, Tantrum was captured by Doctor Robotnik's forces and made into the organic battery of a Buzzer. He was eventually freed from the Buzzer by Tails in the Spring Flower Zone, at which point he immediately threw a tantrum because he was lost, only stopping when Tails agreed to take him home. However, before they could fly away, they were accosted by the bounty hunter known as Fleabyte, who wanted to hand them over to Robotnik for the reward. While attempting to escape, Tantrum fell into a deep pot-hole, and Tails was forced to follow him.
Once underground, Tantrum started screaming that Tails had not looked after him and that he wanted to go home, but his screams were so loud that they caused a cave-in and blocked the exit. As they attempted to find another way out, Tantrum oscillated between calling Tails "useless", screaming for Tails' help when he was in danger, or praising Tails with hero worship. (This led Tails to wonder if that's how he sounded to Sonic.)
Tails and Tantrum eventually made it out of the caves, only to be immediately accosted by Fleabyte, who had been tracking them overground. Although Tails managed to break free, Fleabyte grabbed Tantrum to use as a hostage. However, he wandered beneath a high rock formation, and when Tails suggested that Tantrum scream for help his loud wailing buried Fleabyte under rubble. Tails and Tantrum were able to escape, and Tantrum was reunited with his mother in the Metropolis Zone.
Tantrum is incredibly immature and frequently throws tantrums when he doesn't get his way (hence the name). He also has a habit of causing problems, then relying on other people (notably Tails) to get him out of them.