Giga Thomas "Pen" (ギガトーマス “ペン”?) is the fourth boss in Sonic the Hedgehog Triple Trouble, that the player will face at Robotnik Winter Zone Act 3. It takes eight hits in total to destroy it and each of two hits make one of small engines inoperable for the mecha.
Giga Thomas "Pen" was created by Dr. Robotnik. "Pen" is an floating dark-blue colored penguin head with a small hatch on its belly and three small jet engines.
The early part of Robotnik Winter Zone Act 3 requires the player to climb up the slopes of an icy hill, all the while being forced to dodge Penguin Bombers Badniks descending from the summit. The player can collect huge amount of Rings during this, though as the player progresses, the screen locks, preventing backtracking.
At the top, the player enters the large hall, where Sonic/Tails finally finds the source of this stream of Badniks: Giga Thomas "Pen", a giant flying penguin head, that spits the smaller Badniks at Sonic from the depths of its cavernous maw. At first, it will float on one place, spitting more Penguin Bombers from its hatch, until the player starts hitting him, as it starts moving on small pattern of back and forth. The player has to time the mecha's spitting attack and then jump into him. The player also has to watch out flames, that come from engines. However as much the player keeps attacking, each of two hits make one of three jet engines shut down.
After doing seven hits and the two side engines shut off, Giga Thomas "Pen" starts to head to the cliff with only one engine being barely active. When the mecha is floating on the cliff, the player has to do one more hit on him, the Giga Thomas "Pen" starts exploding and falls into the depths of the pit. After this, the player falls safely to the pit and meets Knuckles once again, who this time activates the switch, that causes an avalanche.