Bulk and Skull shouldn't try to put food like a sandwich in the time capsule, because it could spoil and anyone in the future who would want to eat it would get sick. The sandwich also looked too big to fit in the capsule.
When the teens are walking to the park, Kimberly's shirt is pink but after Billy hands them a shovel, her shirt is a yellow/orange color and then switches back to pink during the fight scene with the putties.