appearances can be deceiving
Appearances do not always convey accurate information. That house sure looks beautiful on the outside, but appearances can be deceiving. What did the inspector say about the foundation? Sure, she seems nice, but appearances can be deceiving.
Appearances can be deceiving.
Prov. Things can look different from the way they really are. Edward seems like a very nice boy, but appearances can be deceiving. Jane may look like she doesn't understand you, but she's really extremely bright. Appearances can be deceiving.