Sometimes on AdSense, it displays ads for AdSense. I'm just wondering, if somebody clicks that ad and signs up, do you get them as an AdSense referral? I'm guessing not, but I've wondered and just want to confirm it.
No you don't get any referral $ for that. It is a CPM ad that Google is showing on your site. If you don't want it, you can add google.com to your competitive filter list in adsense.