Frogs (amphibians) and crocodiles (reptiles) are poikilothermic or cold-blooded animals. Temperature is regulated mechanically and not metabolically by moving in and out; the heat source is usually the sun.
Cutaneous respiration occurs in frog but not in crocodile
The eggs of crocodile are amniotic while those of frog are anamniotic (no amnion)
Fertilisation is external in frog; internal in crocodile