The standard Japanese dialect "R" is a voiced alveolar tap/flap. A flap is like a stop/plosive(/p/, /t/, /k/), except the passage is closed for a much shorter time. Flaps are often found in non-southern American English as allophones of /t/ and /d/, such as in bitter, water, potato, latter, and ladder.

In short, it is never an American English "R" sound.

Sometimes, such as when spoken slowly, or at the beginning of a word, or in songs, the Japanese "R" may be pronounced as a lateral "L" sound by some people.

In the mostly extinct dialect of downtown Edo, the "R" is sometimes trilled. In anime, a character may switch to this form of pronunciation when shouting angrily, to depict a rude Edokko stereotype. One thing to keep in mind when watching anime is that the Japanese spoken in it may not accurately depict vernacular Japanese.