The Possible "Cheater", Cassio.

Iago, that squirrel I talked about last time, has the idea that Cassio is also attracted to Desdemona.  It might just be one of the "Iago" rumors, but it also might be true.  Some quotes like this one
"O behold […] You men of Cyprus, let her have your knees,
Hail to thee lady! And the grace of heaven,
Before, behind thee, and on every hand,
Enwheel thee round. (2.1.8)

That quote, from Cassio, shows his attraction towards Desdemona.  I'm not completely sure if that was just him being a gentleman or if that was for real.  Before that, Iago said he wanted to spread a rumor that Cassio was attracted to Desdemona so Othello would get mad and Iago would get the moor's job. If you read this Shmoop summary of him you might have some of the story spoiled for you, but it has some great content. (Click the picture for the link.)

Cassio in a new version of Othello.

Another Shmoop this one is a timeline of Cassio's role in Othello. P.S. Sorry I couldn't find another funny picture of Cassio. (Click the picture anyway.)

This video shows a great representation of both Cassio and Iago in Act III Scene 3.