Done this before especially when the bulge was especially huge.
One three occasions...over more than a decade...I've met some great big pussy size queen women because I noticed them and noticed that the women with them were showing a huge bulge. Two of the guys were flaccid when I first saw them and met them latter. But one guy...who was working the closing shift at a Starbucks and on his break.. got up to go to the men's room after sitting with the woman that was with him and he had a full very thick horse dick erection stretching his pants running down leg ....(not his wife but has I later learned she was the mother of his past high school girlfriend who was now off at college while he was working the evening shift at a Starbucks).
One of the other guys I saw his very, very BBC hanging down at a urinal next to mine in in a church choir/gym changing room. He saw mine and we chatted for a moment. I had seen his wife and kids in the church...some of the biggest breasts I have ever seen. Custom made bra size. I mentioned where I worked out at night after midnight. Sure enough, about a week or so later, he showed up at my gym and we met again and saw me change again because he had told his wife...naturally...and that led to the three of us meeting many times. He has a huge thick and long bbc and she had never seen anyone longer than her cleavage before meeting me. She's definitely a BBW but WOW, what a libido to match her boobs and her now bigger pussy. We still get together at least twice a month.
The other woman I first saw her and her husband leaving a restaurant I was in. She was also very busty...LOL...I have a type...LOL...and a hot late 40s milf. But trailing after her was family and her own horse dicked husband showing a thick cock hanging down his thigh. Small local restaurant...so I kept going every week that night and a few weeks alter saw them again. I noticed that when they finished eating, before paying and leaving, every time she went to the ladies room...returned...and he went to the men's room and when he returned they paid and left. So I showed up again the next week, there they were...just the two of them. When she went to the ladies room, I wen tot the men's room, used the only stall to unwrap myself, then with my pants down to my knees took the two steps out of the stall to the urinal next to the wall and left the other urinal next to me empty. About the time I did that, he walked in, saw me in front of the urinal and stopped in his track's and jaw dropped. He went to the r urinal and then we visited for a few moments while we both emptied our bladders. He and I left together, I went to my table and he to his. He must have told his wife because when they left and walked by my booth she looked directly at me and he was again walking behind her and he nodded and spoke a "have a good night" as he walked past. The next week I was back, they were already there, and then asked me to join them. She is spectacular and I see her often when she comes over for fun and frolic and sometimes I go there to have her with me and his too and he likes to watch also.
He has a very , very thick one that is also enormously long too.
So seeing another hugely endowed guys bulge has worked out for me three times. But it was mostly my attraction to the women and they were with guys who had huge dicks.