This section of the film re-uses animation very heavily. You can tell that the people behind this film are doing everything they can to hold down the costs. As sequence director Gerry Geronimi got his start in silent animation, where re-use was a standard tool, it's no surprise.
Shots 54 and 57 by Ollie Johnston use the same drawings of Pongo. Shots 52 and 66 by Johnston use the same drawings of Pongo. Shots 81 and 88 by Marc Davis use the same drawings of Anita, though 88 is 81 in reverse. Shots 50,56 and 69 by Milt Kahl use the same drawings of Roger. The Roger scenes are a repeating gag, with him about to light his pipe and failing because Pongo's leash pulls on his arm, but the gag could have been put across without resorting to re-use.
In addition, Hal Ambro's animation of Anita in 111.4 and 113 has always looked to me like it relied very heavily on live action. There is something about Anita's proportions and timing when she laughs that have the look of rotoscope to me. Shot 62, where Roger zigzags along a path, is also credited to Ambro and also suggests rotoscope, though not as strongly as the Anita scenes.
There is a continuity error regarding Roger's hat. In shot 93, the hat is clearly left on the bench as Pongo pulls Roger towards Anita, yet in shot 94, the hat is back on Roger's head.
While some corners have been cut, there are some amazing scenes here. Shots 79, 83 and 85 are Pongo romping with Roger's hat in his mouth, animated by Milt Kahl. All I can say is that Kahl seems to be showing off as much as Pongo. Kahl revels in his ability to draw Pongo's dog anatomy from odd angles. Take a look at these:
(Click any image to enlarge.)
This is what it looks like when an animator brags.
Frank Thomas's shots of Perdy and Pongo in 114.1 and 115.1 are (the pun is unavoidable) unusually frank. Perdy's smile is saying "yes" to a tryst. Pongo actually licks his lips in anticipation of what's to come. While the sexual content of these shots goes unnoticed by children, there's no question their parents read the shots as intended. What's really funny is that the next sequence starts off with the dogs getting "married," so their lust is okay as it has been sanctified by clergy.