If you'd like to cull your flock of Twitter followers by removing any fake accounts, bots or inactive accounts, have a look at this Digital Inspiration post from Amit Agarwal. He has written a Google Script that scans your Twitter followers and finds those who use the default egg profile picture. The thinking being that any real user on Twitter will have replaced the default egg with a real profile picture.
After the script runs, it will then email you a report in the form of a Google Spreadsheet that shows all of your egg followers with a few columns of useful information, including when they joined Twitter, how many times they've tweeted and how long it's been since their last tweet. Each egg follower on the report features a linked username, which you can click to open their Twitter page, at which point you can block them from following you.
On Agarwal's post, he provides a link to his Google Script and outlines the four simple steps needed to run the script and generate your egg report. If you have a large Twitter following, it may take some time for the report to show up in your inbox. You'll get an email immediately confirming the report is being generated, followed some time later by the actual report. In my case, it took 13 minutes to scan my roughly 1,500 Twitter followers and identify the 135 eggs that follow me.