When Mac falls from the tree, the strap from his backpack comes off completely, but when Goo fixes it, the strap is just ripped in half.
In Go Goo Go, Goo has a band-aid on her knee when she has a bruise. When she starts making a bunch of imaginary friends, the first shot of her is without her band-aid, and the rest are with.
The episode Go Goo Go starts out in the middle of June. The next day, Mac is holding a bunch of school work even though he's supposed to be out of school.