Ratty

Ratty (チュートン) is a rat virus from the Mega Man Battle Network series that attacks by launching mini versions of itself (Rattons) that move in a straight line along the ground towards the player. These Rattons can turn once to seek its target. Rattys move around very fast, with stronger variants moving faster. When its HP is low enough, this virus opens its eyes widely and starts to move and attack much faster (the speed of the projectile remains the same).

Ratty
Rattys are orange with an orange head. They also have a red light on top.

Ratty2
Ratty2s are brown with a blue head. They also have a dark orange light on top.

Ratty3
Ratty3s are gray with a gray head. They also have a blue light on top.

RattyΩ
RattyΩs are dark gray/blue with a dark gray/blue head. They also have a green light on top.

Battle Chips
Ratton (ラットン) is the series of Battle Chips obtained from the Ratty family.

Anime
The normal Ratties make a regular appearance throughout the MegaMan NT Warrior anime series as viruses that the characters must defeat to proceed. They are often found in an army of many types of viruses, and are usually taken out within a single shot.

Trivia

 * Its Japanese name is derived from チューチュー (chūchū), the sound of a mouse squeaking.