I've seen it happen multiple times, especially in more corporate jobs.

I try to very specifically mention who came up with ideas even if it's my work for this reason.

Another common one is not wanting to ask simple questions in meetings as it makes them look less intelegent. While I ask every stupid question I can think of to be sure and look like I'm invested.

My advice is talk to your manager about things like that instead of helping. I know it feels like a dick move but it's not your job to help someone else with basic stuff.

Something along the lines of "I think John may require more training as I'm having to help him a lot with simple things. I'm happy to do it but my deadlines will need adjusting"