Tonight's Best TV

A Daily Guide to Notable Shows by Clark Collis

8:00 CBS

The Big Bang Theory

Last year Bob Newhart won his first-ever Emmy for portraying kiddie-TV host Professor Proton on The Big Bang Theory — and the fact that the main body of this episode starts with news of the character's demise may not prevent the TV icon from adding to his trophy collection. While the regular cast members all competently hit their comic beats, ''The Proton Transmogrification'' is once again essentially the Bob Newhart show, as the ¬professor returns on Star Wars Day in ghostly form — and Obi-Wan Kenobi costume — to gleefully muck about with a lightsaber and offer Sheldon (Jim Parsons) advice: ''Always get a prenup.'' B+

8:00 NBC

iHeartRadio Music Awards

Internet pop-music hub iHeartRadio has its own festival, so an awards show was the next logical step. Fans can vote via Facebook and Twitter for the usual suspects (Justin Timberlake, Rihanna, Eminem, Drake, and Imagine Dragons are up for Song of the Year); performers include Pharrell Williams and Shakira, with or without her revolving chair. — Kyle Anderson

8:00 The CW

The Vampire Diaries

Markos' plan to break the witches' curse puts Stefan and Elena in danger, so Damon suggests they hide in a remote cabin. Great idea. Nothing bad ever happens in remote cabins.