Apple Tree Pests
You have aphids...and lady beetles! The little alligator looking thing is a ladybug larva, and the orangier one is the pupa form. They are feeding on the aphids, so you don't want to get rid of them!
The aphids are preparing to move to their summer hosts and won't be a problem much longer, but in the meantime, you have a good natural control working for you.
Next year, if you can spray the tree with dormant oil before it leafs out you can prevent or at least minimize the aphid situation. The dormant oil smothers the aphid eggs that overwinter in crevices in the bark.