Tension

If he carries a frying pan around he can also cast iron

So, interesting thing in 5th edition, Paladin spells don't actually come from a deity, but from their faith in their oath. Clerics are the only ones whose power comes from a deity

Where does it say a Warlock has to sell their soul? And it definitely doesn't have to be a deity. They can make a pact with a unicorn.

Warlock just sounds so much cooler than wizard

They're small, can't grow bears (usually). They're also generally somewhat playful and shy. They generally fear things they don't know, which can be seen by the fact they don't travel far beyond their homes. They are pretty care-free and not bothered by external event, and fairly joyful. They live relatively simple lives and generally seem to be easily amused.

They don't behave exactly like children, but they do have qualities we associate with children. That, plus their physical characteristics, I'd say childlike is a decent description, particularly if you're just trying to insult someone for hanging around them.