Sunnycide is an egg-like boss in Mario & Luigi: Partners In Time that is found inside Yoob's Belly. The name is based of the way some people eat eggs for breakfast: sunny-side-up.
History
Sunnycide was created by the Shroobs to used Yoob to eat up other Yoshi. Inside of Yoob, Sunnycide runs a large factory that transforms Yoshis into eggs. The intended plan was to then hatch up the Yoshis into more Yoobs making a Yoob army to help aid in world domination for the Shroob race. However, Sunnycide was soon defeated by Mario, Luigi, Baby Mario, and Baby Luigi and the giantic Yoob was shut down for good.
Battle
Sunnycide has many attacks in battle. It mainly attacks by hurling eggs at Mario, Luigi, or the babies. It can also suck up either one to heal it's own HP. When Sunnycide is flipped over it's back, it poses two new attacks which involves pulling a rope that can either: turn of the lights and a Boo attacks one of the group or summons a trap hole that will pull them under.
Tips
The key to defeating Sunnycide is to flip it over on it's back. This can be done by destorying the eggs that are near it. Destorying the eggs results in a Yoshi running out from it and is seen pushing a rock on the top of the screen. After five Yoshis have been freed, they will push the rock onto Sunnycide causing it to flip over. This is Mario, Luigi, and the babies' chance to unleash their strongest Bros. Items to quickly take down Sunnycide.