I have had a few player’s Wizards cast the 1st-level conjuration spell Find Familiar, but then flip through my copy of the Monster Manual for the next 2 minutes. The main issue is the 15 beasts the familiar spirit can embody are pretty varied.
You gain the service of a familiar, a spirit that takes an animal form you choose: Bat, Cat, Crab, Frog (Toad), Hawk, Lizard, Octopus, Owl, Poisonous Snake, Fish (Quipper), Rat, Raven, Sea Horse, Spider, or Weasel. Appearing in an unoccupied space within range, the familiar has the statistics of the chosen form, though it is a Celestial, Fey, or Fiend (Your Choice) instead of a beast.
Here is a PDF to the cards: Find Familiars Cards
Here are images:
I should note, I let players use all the abilities rather than just “eyes and ears” for their action cost (houserule).