I don't know if Mark Tatulli feels the same way. Regardless, Andy Capp makes a cameo in his strip Lio on February 6, 2016.
Tatulli's played with the panel borders before, and characters from other strips have entered through them. This one is especially nice because Tatualli's rendition of Andy Capp is spot on. And note the way the panel's layout. There's no border around Andy Capp because, of course, he's outside Lio's strip. Having one of the panel lines serve as part of the trap is just genius.