"It's a wonderful, full-bodied movie," Allen told ET's Leanne Aguilera at Fox's Winter Television Critics Television Critics Association gala at The Fig House in Los Angeles on Wednesday night. "They've taken this in a direction that is spectacular."
"Both Tom and I, who met yesterday for our little guy's lunch, we were both very very affected by the end of the movie," Allen, 65, reflected.
"So much so that he had turn around. He couldn't even deliver his end of it, [and] I couldn't deliver my end of it," he added, referring to their final group recording session together.
This latest film in the beloved Toy Story series, which serves ostensibly as a road trip movie, sees Buzz and Woody reunite with Bo Peep (Annie Potts), who makes her first return to the franchise since Toy Story 2 in 1999, and has become a more world-traveled and adventurous toy in the interim.
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The 'Toy Story 4' Trailer Is Here!
"These writers have done something amazing. The characters they've developed are amazing," Allen said, teasing a bit of the film's story. "It's a love story between Tom and his love interest… and then Buzz has to make a decision on how to move on with his life cause Woody's making some different decisions… It's so funny and so bright and so interesting and so affecting, towards the end."
Allen also reflected on the impact the series has had on his and Hanks' lives since they first worked together all those years ago, sharing "This has been over 20 years of he and I doing this, and it's made an impact on both of our lives our families lives."
So what impact might that have on the future of the series? Allen admitted he's not sure what kind of involvement he and his longtime co-star will have when it comes to later installments, but explained how that the series still has a lot to offer either way.
"Once you've gotten to four, you're passed that trilogy [point], so I don't see any reason why they wouldn't do it, certainly," Allen shared. "If you ask me, I'd say do five."