A good ad can make you laugh, but a great ad can make you cry. By that standard, Purina and Leo Burnett's "Inside Every Good Dog Is a Great Dog," set to the Tony Rogers song "Great," is a pretty great ad. The spot has been airing during coverage of the Purina-sponsored Westminster Dog Show, and the real-time response has been overwhelmingly positive. Actually, it's impressive that so many people are able to type through their tears. Such an emotional response is always appreciated by advertisers, but especially so in this case, where Purina is replacing longtime event sponsor Pedigree. Rogers is selling the song on his website, and will donate all proceeds to Pro Plan's Rally to Rescue, a charity that helps find homes for dogs. Meanwhile, here's a sample of Tuesday night's warm and weepy tweets about the ad:

• "This 'I Could Be Great' Purina commercial is so good. I cry every time it comes on." —@Kittywink

• "@purina – Your 'I Could Be Great' ad… Thank you." —@Unchainedfoodie

• "Hope Purina stops showing this ad soon because I get misty eyed every time I watch it. :(" —@Ladewig

• "Thank you @Purina for a great dog ad that made me cry but in a good way!!" —@featherchick

• "I don't agree w/Westminster's decision to end relationship w/Pedigree, BUT these Purina commercials are really really cute." —@nicholeaileen

• "How many times is this Purina commercial going to make me cry?" —@melpaettie

• "I'm not tearing up at that Purina commercial. It's just dusty in here I swear!" —@310tojoba

• "@Purina, you must provide Kleenex with this commercial, because OMG. My heart." —@kimt205

Credits after the jump.

CREDITS

Agency: Leo Burnett/Arc

Client: Nestle Purina

Producer: Dani Jackson

ECD: Tony Rogers

Editorial Company: Whitehouse Post

Editor: Jennifer Dean

VFX Company: Carbon VFX

VFX Producer: Frank Devlin

Telecine Company: Filmworkers Club, Chicago